I haven't had a period in 76 days

Ok so last year I've suffered from not having a period for like months, then I eventually went to the doctor and he said my uterine line was really really thin, so he prescribed me birth control to thicken it up. It worked I guess because my periods started back. It was all cool and fine, but when my periods came in they were so painful and I was really miserable 😭. So I stop taking the pill for a while because I couldn't take it. Here it is I no longer have a period again. What could be my problem now???