I had unprotected sex and the next day i had a little bleeding but i don't start my period until sunday. i'm on the pill but could i be pregnant?

When in doubt check: if you are 100% compliant with your pill you are likely not to be pregnant but it is not a sure thing. ovulation ( and thus the optimal time to conceive-get pregnant) is day 14 of your menstrual cycle. if your period is coming up and you had sex a week or two ago you would be in that time frame. when in doubt...check. take a home preg test if your menses does not come as expected.