Sometimes I really don’t know if I committed a mortal sin or not, I have a doubt whether there was full consent and advertence, for example.

I can only go to confession on the weekends (there’s no weekday confessions) but I have access to daily Mass and I’m able to go to it. So sometimes it can happen at the beginning of the week and that would mean I wouldn’t be able to go to Communion for the rest of the week till I confess. 

Many times I’ve gone back and forth and decided there was no mortal sin based on previous confession feedback and based on what I know of when it becomes mortal, so in these situations, I’ve gone to Communion. 

But then I always have the thought in the back of my mind: should I really have gone? Was it really not a mortal sin? Was it a sacrilege? Obviously each time I hope I wasn’t in mortal sin and made several acts of perfect contrition but of course I know perfect contrition is not enough to receive Communion if you’re truly certain you’re in mortal sin. 

So I always wonder if I did the right thing because obviously I don’t want to commit sacrilege but at the same time I don’t want to be depriving myself of the benefit of Communion unnecessarily and I always wonder if it’s the devil trying to make me not go. 

I would ask your confessor about it. 

When I have had similar doubts, my confessor has assured me that it is most likely that I was not guilty of mortal sin if I was uncertain of it and condoned my having received Communion. But, again, I would advise seeking counsel from your confessor. 

When in doubt DON'T GO.  If there is even the slightest chance of committing a sacrilege DON'T DO IT.!
As for feeling good after you've gone to Communion....the devil can do that too.  Feelings or any good things after are not a good way to measure worthiness.  the devil would certainly reward you for committing a sacrilege.
Best to work on not committing the possible mortal sin instead of worrying afterward.

I didn’t mean “feeling good” as in emotionally etc.

I meant being objectively better, like avoiding sin and doing more virtuous things.

As long as that doesn't let you fall to the sin of pride.
When the devil can't get a devout person to sin he helps them increase in virtue to
trap them in the sin of pride.
We are fighting for our eternal souls against the master of deceit.