What could cause this?

OK i'm what people call a really big worry wart, but last month i was a day late and had a very spotty period (I never have those despite what's going on) i actually had some spotting seven days before i was due but for a couple hours, then again a few days later, i cramped a bit for three days before i started spotting more heavily(what i'm considereing my period) and then a little after. I spotted for the normal period duration, but as i said it was no where near normal. i took 2 HPTs and both were negative. Then this month i was 3 days late, but the day i started i had severe cramps which went away after piggy backing ibuprophen, the flow was pretty regular for day one but now day three and it's going on and off and Day 3 is supposed to be my heaviest. I havent cramped since the first day but i've had some small clotts. My question is what could be casueing this? I'm worried it could be a number of things like going through menopause early (I'm only 20) or that those tests were too early and i am/was pregnant and my body is trying to have a miscarriage or something. I know i need to schedual an appointment with a doctor now, but i just wanted to see what you guys think it is since i cant get into the doctors for a few days and i'm concerened.