Need advice

Alright so basically I had my period from the 5th to the 9th of February And on Valentine's Day and on Wednesday I had sex (with a condom...but I'm not on birth control) glow said its only a 3% chance of pregnancy. I also was ontop just grinding not having him in me or anything. Anyways. Today I'm having very light bleeding... Any tips, advice or idea what could be happening ?