Possibly pregnant..what do you think?

I think I may be pregnant. I had sex then about a day or two later I got my period but it was a week early (its never been early in my life otherwise I'd think nothing of it) and it was about 2 days shorter than normal. By the third day I didn't even fill a tampon. Now its been 12 days since I had sex and I'm feeling tired, cramps (as if I'm about to get my period but I'm not), nauseous after I eat, gassy, bloated, sensitive nipples (not too bad though) and overall I just feel like somethings different. I've been feeling this way for a few days now. I've heard women can ovulate late or even while they are on their period, everyones different and I had been stressed out during that time and think I could have ovulated late or when I was on my period (and if I did then the sperm could have fertilized the egg when I was on my period because they can live inside of you for a few days). Do you think its possible that I'm pregnant?