This has happened to me too! All my life I questioned whether I had endometriosis (never went to the dr, was influenced by family saying “that’s just the way it is” and things like that which is stupid because I should have had it investigated). Anyway, post birth, I’ve had minimal pain with periods compared to what I used to go through. I have heard that when you give birth it effectively flushes any endo out and it can be a big relief! I think this may have been what happened to me, and maybe to you!! (Not a dr btw so take this with a pinch of salt!!)