Cramps a few days after having sex?

I had unprotected sex on Sunday and since Tuesday and now Wednesday I've been having slight pains under my tummy around my waist line. its not like unbearable pain but it comes and goes. Like it will come for a few seconds and than leave and than a few minutes start all over again. it feels like pressure is being put in that area around my waist line and just comes and goes. it doesn't hurt major but it still is unpleasant. what does this usually stand for or mean? could it mean my bodies making room for a baby is I'm pregnant or what? I'm already wondering if I'm pregnant since like I said I had unprotected sex so could this be a sign? 'cause this is a different kind of cramps from my period and my bodies never felt/dealt with this before. do you think I'm pregnant or am I just worrying for nothing. please give me as much of a solution/ answer as possible, thank you.