Could i be pregnant? Advice please.

I had sex with my boyfriend, and usually he pulls out, but he came in me about 2 weeks ago. I went to the bathroom the other day and when I wiped I saw blood and thought I just had my period. It wasn't. The tampon had no blood at all. I have cramps like I should be getting my period, and I just feel utterly awful the past few days. Am I being over paranoid or could I be pregnant? I know it cant really happen when your not ovulating but I'm still worried.