possible miscarriage?

Hi, I am seventeen years old. I recently feared i might be pregnant although it had only been about 3 weeks after the incident. I was having a lot more pain than was normal for me before a period, but then i ended up getting my period, although it is incredibly irregular. It is very heavy and painful, and I even have a strange solid discharge coming out with it. I read something somewhere about possibly still having such bleeding even at the beginning of a pregnancy. Or that it could be a miscarraige I feel that it would have been way too soon for something like this to happen but I am still unsure and terrified. I don't know much about this at all. I just need some sort of information so I can know whether I should worry or not.