A friend of mine once was in a similar situation. She had unprotected sex and her period was late and barely there and MUCH different than usual. Turns out she wasn't pregnant and it was just a coincidence. So maybe that's the same case, but of course, if you continue to feel strange I'd see a doctor and take a test there or take another brand test. I agree that if you are in the age range, it COULD be menopause, but if you are not that age, is there any medication you are taking? I used to take anti-depressants and when I stopped taking them, I would get hot flashes and get night sweats all the time. And of course, like you said, it could just be hormones. Just to ease your mind, I'd try taking another test soon or take one at a doctor's office. If it's not too late, you can always take the morning after pill, but I'm assuming it's been over 72 hours since the unprotected sex.