Is Pregnancy Possible Despite Being On Birth Control Pills?

I took bc for two weeks before i stopped. Had withdrawal bleeding for about a week, then my period came on the regular time right after withdrawal bleed. I had unprotected sex about three days afterwards, my bf came in me. Its been a week now and no period,, i can feel something at my abdomen, sensitivity to smells, cravings, extreme backaches, tiredness and occasional sore breasts. SO far took two tests n came back negative.. I don t know whats going on, can i still be pregnant?