Implantation bleeding or regular period?

Okay so I skipped my last period (I'm on the pill) because I was on vacation and didn't want to mess with it. Today was supposed to be the day I started this months period, but I hadn't felt it coming at all. My boyfriend and I had sex because I heard that can induce your period and when we were done there was blood ....I'm just confused as to what kind of blood. It looked like the beginning of any other period for me (dark).  I put a tampon in for 8 hours and took it out and it was still like, half dry. Soooo I don't know what the heck to think at this point. I Haven't felt any cramps or anything yet. Would sex have induced implantation bleeding too?