My sister had the same thing like you and she's not pregnant. She been trying to conceive for so long unfortunately unsuccessful. The best way you should go to see gynecologist. They will advice you.
In fall of '08 (August - November) I had the same thing happen. I took a pregnancy test every couple of weeks and never got a positive answer. I too was having bad pregnancy symptoms. My breast grew a whole cup size, and where very touchy. I put on 5lbs, and boy was I nauseous. On November 12th I began to bleed and had bad cramps (which isn't anything knew since I have sever cramping normally). Everyone told me it was from stress, that I wasn't pregnant, that was just having an irregular period (I track them so I know this was wrong). I really believe I had a miscarriage, but then again I can't be sure.
I think you should go to a doctor. I have no insurance and because of that and other issues it was impossible for me to go to a doctor, or any medical facility.
If you are in America go to Planned Parenthood or to your GP. Don't wait to long, it might be to late.
u might need a blood test to see if u r pregnant or not if all ur hpt is negative