I started my period when I was 14. I had it for four months, regular. And then it stopped for two years. I went to the doctor, they tried to get me on birth control; it turns out I am allergic to a chemical in it and it causes 'rapid heartbeat' anyways, My period is almost noraml now, just a little heavy.I started having sex when I was 15 but I never did it on my period. I did however, do it on my period for the first time last month. Well, this month I was not only 14 days late BUT I am having horriable cramps. Sometimes it hits me and I can't even breathe, I haven't slept in two days. I took two pregnancy tests (because not only was i late, but my nipples where also extremly sore/tender and bright pink) they both turned up negative. So my question is number one, why are my nipples so bright pink/tender and sore? Number two, they say you get cramps because your uterus is contracting... well, your uterus is on your lower stomach, so why are my cramps below my ribs? And did having sex last month have anything to do with this?