Some women do spot when it is time for their period. Have you gotten it yet? It sounds like you had sex around the time when we ovulate which is midway through our cycle. Also, the above is a bit inaccurate. You can get pregnant during a fertile window which is ovulation that lasts up to 48 hours and then sperm can live for a week prior to that and can impregnate you. Also, some women have, even though it is rare, a second ovulation. You can't count on knowing when you ovulate and definitely, the week before your period is your fertile time. Anyway, buy a test and let us know.
I don't think you're pregnant dear since you are bleeding a bit which is a sign of your period. You can only really get pregnant once at a certain time and that's when you're ovulating so it depends if you were ovulating or not. Save yourself the anxiety and get a pregnancy test. Wait another day or two to see if you get a complete flow. If you don't, take the test and you will have an answer. By two tests just to make sure.