I'm 20, and have had my period since I was 13, and for the past five years or so, it's been perfectly regular, to the point where I know exactly what's going to happen with my cycle. My bleeding is usually fairly heavy for five days, with bad cramps, back pain, and all that jazz. However, my last period was four days early, and started off spotty and brown-ish pink-ish, then was red and heavy with clots for the next two days, then faded to a light pink-ish on the fourth day, then stopped. I was worried it was implantation bleeding, because it fit the time frame of my boyfriend and I's relations (we did use protection), but then a few days ago, at the start of my fertile period, I experienced the familiar feeling of ovulation. Now, the day after I was scheduled to actually ovulate, I'm having moderate cramps on what feels like both sides and a decent amount of reddish-brownish blood. I was wondering what's going on here? Is it pregnancy, or endometriosis, or is my cycle being odd?