HELP?!

Dumb question but can you start showing symptoms after a week of having sex?? Im on the pill and my SO and I had sex 2 different days and both he came inside me. I have been on the pill for about 3 mos now and thought i would be okay. But now im having constant urination like every 20 or so minutes i swear I'm not sure why. Is there anyway this is my body telling me im pregnant? Im not drinking a lot of water either and im usually really good at holding it in but Monday i tried and it hurt a lot to hold in like pressure. What could be happening? Edit: im not having any pain while urinating or having signs of UTI :/