Pregnant or not? I can't figure it out!?

About 2 weeks ago, I had my period..or so i thought. It only lasted 3 days and was fairly light. I'm pretty regular and I've been using the pill. I'm not always consistant with it though. I've been slowly puttin on weight (about 5lbs in 3-4 weeks) and i havent extremely changed my diet or exercise. For about a week now, I've been feeling awful. My are sore, i have frequent headaches, and I get sick to my stomach EVERY time i eat, no matter what, when, or how much I eat. I get bad cramps in my back and sides and I'm bloated and gy quite often. I've been really irratable, but I also stopped smoking about a week ago too. I took a pregnancy test 2 days ago and its negitive....so what the heck is wrong with me? I can't keep getting sick....i love to eat too much! lol Some help please!