We've been having unprotected sex I had my last normal period the beginning of June then I didn't have my period till August 3rd and it was only like 4 days, my periods are usually 7 days. Well it's sep 13 and I haven't had one since the brief one in August. Ive been nauseous and I've been having heart burn every day now for the past week. I'm extremely tired and I I've had a few headaches. I've taken one pregnancy test two days ago and it was negative. Can anyone tell me what's going on?

Stomach virus, flu, other illness, could be a dozen things. Normally you will have to be at least 14 days late to start testing, so best to even wait about one more week and do the test again.

Also do test first thing in morning as soon as you wake up, first urine of the day