the f is going on?

Okay guys, so being the 18 year old dummy I was I thought getting the shot was a good idea. Well I found out twoish months later that I had been pregnant before I got the shot and I had miscarried (confirmed by doctor) and that was in October. It's now July and I still haven't gotten my period. I know it could have messed up my schedule but three months without my period? I've taken a test which came up negitive a few weeks ago but I have a condition, (hypothyroidism) which means my body doesn't send out the correct hormones and it can cause false negatives ofter. Soo basically I need adcice, anyone else had this happen? Oh, and I'm these three months I've gained almost 15 pounds 🙄