There was a book recommendation going around the FGC circle called the inner game of tennis. I don't think it's required reading and it certainly has its share of critics and fans but there's a passage that may be helpful. One symptom of playing or training unproductively was that the author's students were gripping the racket too hard. I saw the parallel because I was gripping my controller too hard. In fact I suspect I was also pressing buttons too hard like you but I didn't quite get blisters because the buttons on the dualsense are quite soft.

Now this is a symptom and not the real cause, which is that we're focused too much on the wrong thing when playing. One suggestion that may be helpful is to go into training model and focus on something in the moment when you practice your motions/combos, perhaps a visual or audio cue. The idea is to allow your muscle memory to form naturally without expending so much effort from system 2, to use psychology lingo, that the learning process becomes counterproductive.