Irregular menstrual cycle?

A little background info- I literally never had a period. I finally went to the doctor when I was 18 and they medically induced a period with a drug called provera and was then placed on birth control to make my body have periods. I had numerous exams, ultrasounds, and blood work done and everything came back normal...basically all the doctors I have gone to are completely puzzled. So throughout the years (I am now 23 and very healthy and active) Ive gone on and off my birth control. When I go off, I get no period at all and as soon as I start back up again, I get my period. So here's where my question comes in, I have been off birth control for the past 6 months-with no period. So the other day I got extremely crampy and the next morning I started my period. I'm now on day 3 of my cycle....and i'm just plainly confused...happy but puzzled.Did my body finally hit puberty at age 23? These doctors are not helpful and I don't know what this could be! I've been worried for years about having trouble getting pregnant in the future and now this gives me hope! Any experts out there? Thanks!