Stopping birth control

So I stopped birth control in order to conceive and we had sex Wednesday and a few other times each time he came inside of me. And last night I started getting really bad stomach cramps so I laid down when I woke up this morning I still had them. I tried pooping but it hasn't helped. Took a pregnancy test last night but it was negative and I'm impatient. Are there any signs that I should look for to know?