If you really believed that the Novus Ordo priests are valid, we wouldn't be talking, right?

In my opinion, the Novus Ordo orders are doubtful and not unquestionably invalid. In this case, I don't think that we are bound to reconfess our sins.

If you really believed that the Novus Ordo priests are valid, we wouldn't be talking, right?

In my opinion, the Novus Ordo orders are doubtful and not unquestionably invalid. In this case, I don't think that we are bound to reconfess our sins.

This, OP the new rite for BISHOPS is doubtful, and doubtful sacraments are to be considered invalid, hence all the Novus Ordo priests should also be considered invalid.

If it were me, I would re-confess, just as if the NO priest was not a priest regardless of whatever anyone else says about NO ordinations being valid. They brought this doubt on themselves, we did not.

Confessing one's sins to the priest is not meant to be a pleasant experience because you must really humble yourself to do it. The priest (who is also a sinner) is himself edified by a good confession.  

That is exaggerated. There are still Novus Ordo priests around, usually retired, who were ordained before 1968. Very few bishops are still alive who were consecrated before 1968.

Right, but there are fewer and fewer, and so it's likely that OP confessed to one of these types.

This is certainly a complicated question.

I've come to the conclusion that there's some gray area here between positive and negative doubt, between subjective and objective doubt.  If I personally hold that there's positive doubt, but many priests out there hold that there isn't, I feel that the doubt is in some gray area between negative and positive, between subjective and objective ... i.e. since there's disagreement out there among Traditional Catholics, objectively speaking, rendering the doubt (try to follow) ...

subjectively objective but objectively subjective .

In other words, I personally hold that there's objective positive doubt, but objectively speaking there's disagreemnet about it, making it objectively subjective (i.e. it's my opinion that's not shared by others).

While you could just submit to Fr. McFarland's opinion (or that of your SSPX confessor), you personally might continue to have your own doubts, and if you went to a different priest, you might get a different opinion.

In general, the faithful are not obliged to be theologians and can probably simply go with the opinion of their confessor.  So based on objective probabilism (about who's right on this issue), I don't think OP would have a grave obligation to repeat those past Confessions, but it would be conducive to his peace of soul if he did.  So one thing I might recommend as a compromise position would be to just go to certainly-valid priests going forward, and at the end of each confession, just make part of a general confession each time at the end (since it's always permitted to mention past sins), until you've "caught up".  You could break it down either chronologically (when I was 1-10 years old), next time (when I was 11-20), etc. ... or by Commandment.  As Father Alphonsus used to say, even the most eventful general confession should take no more than 10 minutes, since there are only 10 commandments.  You could just mention a sin and a number, without any more detail than that.  Of course, with general confessions, numbers can be hard to come up with, so maybe a frequency of sin.

That's probably what I would recommend to OP, to be at peace, since you've had a confessor tell you there's no doubt and that you can, in the practical order, proceed on his advice, but then for your own peace, just gradually (without feeling a strict obligation), supplement future confessions with a partial general until all put together you'd have effectively made a general confession.

To sum it up, while you might have your opinion, the faithful are not obliged to be theologians (adjudicating the validity of Sacraments or even adjudicating between the opinions of different priests) and can in good conscience accept the advice of a confessor (even if that confessor might, in your opinion, be wrong).  So I would hold that you're not under strict obligation, given your status as lay faithful, to adjudicate the question of validity or to adjudicate between the opinions of different priests, but I would recommend going forward to confess the past sins little by little at the end of each confession going forward until you've "caught" up, so that you could be at complete peace.

OP, I was going to suggest asking your priest, but then realized that that priest probably thinks the New Rite orders are valid.  Do you have access to /Can you contact a Resistance or Sede priest?  If so, I would get their opinion.  I think they would probably recommend some sort of general confession. 

What's the point of getting another opinion from a different priest?  That puts a layman in the position of adjudicating between the opinions of diferent priests, and so therefore it's meaningless to get different opinions (since you know they're out there), and it would ultimately come down to your own opinion anyway, at the end of the day and in the final analysis.  I believe I recall Bishop Sanborn stating that the faithful could just go with the opinion of the priest they approach and have ready access to ... and are not obliged to go "opinion shopping" until they get one that conforms to their own ideas.  At that point, you might as well just go with what you think, since that's what it'll boil down to anyway if you go from one priest to another getting different opinions.

OP already KNOWS that there are differing opinions about the matter out there.

I should have been clearer. 

Assuming the New Rite of Ordination is doubtful/invalid (which is what I think the OP really thinks), find out what a priest who thinks similarly would think about what to do with past sins confessed to a NO priest.

So far it doesn't sound like the OP has spoken with a priest about what he/she needs to do assuming the NO ordination is doubtful. 

I wasn't referring to getting another opinion on the validity of the rite.

I went through the same questions when I cam over from the NO church to the SSPX.  I did some very sinful acts that I confessed to the NO priest and was literally sick to my stomach when I realized those NO confessions MAY not of been valid.  I asked an old aged SSPX priest about this situation and if I really needed to confess those sins again and he said no.  He said my intent was there and that the next time I received absolution from a traditional priest all those sins along with the ones I currently confessed will have been forgiven even if the NO priest was not valid..    I also must tell you though, that over the years being with the SSPX, I still, gradually re-confessed those sins, not because I felt they weren't forgiven, but because I wanted the act of humility to offerup for things and intentions.  It was not an easy thing to do, but I did it and I felt so go after I did.  Such peace I have now. I to this day re-confess sins from the past for an act of humility and I tell the priest why and they always say that it's good to reflect back on things, not that you dwell on them, but to appreciate and trust the sacraments and realize how far your have come with Gods Grace. I can also tell you that I can now go into the confessional and continue to re-confess anything with such ease.  I think this is grace! I realize no matter how bad the sin, no matter how embarrassing the sin, the priest doesn't care.  The worse it is, the happier they are for you that you are there confessing. So to sum things up, I don't think you need to re-confess, but at the same time, if you do, the grace that comes with reconfessing will give you such peace of mind and soul and even more grace that will help you with future confessions!