Help!!

I had unprotected sex last Thursday. I've only had sex once before so this time around I couldn't do it for long because it still really hurts. Well anyways I know he did not cum, for obvious reasons but I'm still paranoid. So my question is.. 
If I had unprotected sex (even if he came or not) would my period that came 3 days after this be a good indicator that I am not pregnant? Or would I still get it even if I was pregnant?
I'm just super paranoid because I'm getting birth control tomorrow and I have to take a urine test and I just really don't want to hear that I am pregnant the day I was getting birth control to avoid this.