Spotting

So me and my boyfriend (16yrs/17yrs) had sex. We have before couple times before (including the first time we ever did). The first I bled a little. Well after that i never bled anymore after sex. Until today when we were at his house. I just got off my period, like the second day being off it. I know this might not be a big deal but I just want to be reassured that theres nothing wrong, please. I can't talk to my mom about this because she doesn't know about me having sex and everything I know about sex I've learned by myself and from Sex Ed. I just want to know if its okay and normal? And how long does it last?