Normally, one would confess this sin by accusing oneself of having actively participated in the procurement of an abortion.

Had you said that, the priest would not have been confused (ie., to declare you used abortifacients is not necessarily the same thing), but it sounds like he did his job, and with some Q&A, figured out what you were trying to confess.

As regards his faculties to absolve the sin of abortion, there can be no doubt that Francis has delegated this jurisdiction to all priests. 

So if your confession was after 2016, all other things being equal, you were certainly validly absolved.

See here for more info: https://www.wnycatholic.org/news/article/featured/2016/11/21/102013/pope-extends-jubilee-mandate-on-abortion-confession

Aside from the sin of fornication the woman in question was also guilty of the potential murder of her child.

Yes, Susanne, I know.

Very complex question, muddied by consideration of whether the 1917 Code still holds or the 1983 Code is valid (i.e. whether you're a sedevacantist).

Did you know before you had intercourse that the woman would in fact take a morning after pill?  If not, then you did not incur excommunication.

If you knew, I believe that the 1983 Code (and JPII's interpretation of it) is actually more strict than the 1917 code, allowing accomplices to more readily incur excommunication.

Also, the problem with such, especially in the 1917 Code, is that the penalty was incurred only IF the abortifacient produced an actual abortion, which you would likely not know.  Some canonists held that the penalty was not incurred unless it was CERTAIN that the effect (abortion) had been produced.

In one sense it's a technicality, but there's no question that grave sin was involved, not only because of the fornication (or adultery) but also due to a reckless disregard for a possible outcome which might entail an abortion.  It's like driving around drunk.  While you may not have actually killed someone (because you were lucky), you were still putting lives at risk and causing the potential to kill someone, like flailing a loaded gun around recklessly and having it discharge into someone (or miss them) vs. taking direct aim and pulling the trigger.

Depends on how much the OP knew and how involved he was in the use of the abortifacient.

Yes, but the OP said

In my past life, I had a woman use abortifacients (“morning after pill”) on several occasions.

The word "had" seems to imply, he had part in organising or planning the use of the MAP: and says several occasions. (I could be reading this wrong. I am sorry if I am OP.
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Praise and thank God he had the grace to repent and confess his sin and is forgiven. He must always keep that woman in his prayers, as there is need for her too to repent.

as a woman I would say that the woman’s sin is by a long way the greater.

We cannot make such judgements or apportion responsibility because we know nothing about either party. We just need to pray for both.

The word "had" seems to imply, he had part in organising or planning the use of the MAP: and says several occasions. (I could be reading this wrong. I am sorry if I am OP.

When the same woman used these multiple times, it's very possible that it was done with the knowledge and perhaps even complicity of the OP.   But we're guessing because it sounds like OP has not provided sufficient detail.

Yes, unfortunately, it was on multiple occasions. Not just once.
I’m just going to ask my confessor about it. I believe I received absolution for this sin because I confessed it. But I’m just gonna make sure.

It’s wonderful that you received and cooperated with God’s grace! Everyday make an act of perfect contrition, no matter the circuмstances involved and the status of your confession, you can be assured that you are in a state of sanctifying grace. You obviously are a person who wishes to abide by the Church’s laws and want to do the correct thing, so in these difficult and unprecedented times I think you are fine. God does not ask the impossible and remember He wants to save your soul more than you do!

My post, I forgot to check the box:

It’s wonderful that you received and cooperated with God’s grace! Everyday make an act of perfect contrition, no matter the circuмstances involved and the status of your confession, you can be assured that you are in a state of sanctifying grace. You’re obviously a person who wishes to abide by the Church’s laws and want to do the correct thing, so in these difficult and unprecedented times I think you are fine as it seems to me you have done your due diligence. God does not ask the impossible and remember He wants to save your soul more than you do!

Thanks Quo Vadis!
I didn’t even question it during the confession or after until yesterday (5 days after my confession). 
I’m sure this is just another scruple and the devil is trying his hardest to discourage me.