Two periods

Samantha

i had my period the 9th of this month & it lasted about 4 days, later on the month my s/o and I had sex on the 17th and he’s not sure he came in me or not but I’m on birth control and then a couple days later Im not sure if I’m starting my period again or it’s just really dark discharge but should I be worried or is this normal ?? I’ve never had my period twice in one month. pls lmk