Miscarriage...?

I am 17 years old, 4 and a half weeks ago I had unprotected sex, within a few days later i started to get dark brown blood spotting, however wasnt due for my period, a week after i had sex i got my period, really heavy and was quite painful and I still wasnt due, my period continued for 2 weeks, being really heavy and for a day or two being light spotting, during this time alot of large clots came out, alot more than usual. I also had lower back pain and cramps and was achy. My period finally stopped a few days ago. Is it possible that I had an early miscarriage?