Really need advice!!

had unprotected sex the day before my period was due which was actually 5 days late I assumed it wasnt coming but it came the day after. it's been 4 days since my period has been it was lighter than usual but did look like a normal period just not as heavy as usual. so yesterday I had light brown watery discharge ( sorry tmi) and really bad lower back ache and pain in my lower abdomen which is very very unusual for me. today I'm still having pains and my boobs are alot more veiny and yesterday I was very moody. is there a chance I got pregnant?