I Am 18 Years Old And I Usually Have Late

I am 18 years old and I usually have late periods. When I do have my period it's very heavy. But I expected my period last week but instead, I've had a brown colored discharge for about a week and a half. I always have brown discharge before I start my period (that's how I know it's about to come) but I've never had brown discharge last this long and I still haven't seen any normal colored blood. There was a tiny tiny bit of red blood two days ago but just enough that would come from a paper cut or something. I've never had intercourse so I don't think I could be pregnant. What do you think it could be?