Could this be implantation bleeding? I am also on birth control and I've been on it over a week

Hi I had unprotected sex with my partner about 3days ago (Friday night) it is now Monday morning and I noticed some very light spotting. Could this be implantation bleeding? I am also on birth control and I've been on it over a week. I started it not this past Thursday but the Thursday before that and this past Thursday was exactly a week I was on it and then I had unprotected sex Friday night. Is there a chance I could be pregnant? My period does not come for another 11 days now so it is really weird that I'm spotting now. Someone please help! Thank you.