Chances of having your period during pregnancy?

Hi there, just a quick question. My boyfriend and I had unprotected sex for about 15 seconds, where he didn't ejaculate, but may have precame, and then put the condom on. This took place on the last day of my period while I was still menstrating slightly (sorry for the graphics) I'm on the pill as well. But what are the chances of having a normal (heavy) period and being pregnant? I took a pregnancy test a day before my period and it was negative, was that too soon though? My period did come afterwards, but I now have slight funny cramps and a white discharge, and it's another 3 weeks before my period. I hear this is ovulating, but I'm unsure? I feel nausious and I have headaches, muscle aches and I'm tired, expecially when I think about being pregnant.. I am severely over anxious though, and I hear those symptoms can be caused by stress? I know this is a long question, but it would be fantastic if someone can give me some advice. Thanks!