hello. since you have anemia and your last period was really heavy, theres a chance it affected your period which made it skip. my advice is go to the doctor and make sure you really are not pregnant. but i doubt you are because if its been 3 months im pretty sure you wouldve had a belly by now. but go to the doctor and tell them whats been going on,most likely they will give you supplements specificly made for your anemia diagnosis
dont worry too much -- i went 14-16 months without mine, got checked and they said it was nothing. a lot of women are very irregular.
You should see a doctor, and between heavy, irregular periods and bad cramps, birth control might be a good option for you. Keep in mind that the first few years after getting your period, your period can be highly irregular. I remember going for 5 months at a time the first couple of years.