Ovulation bleeding or Implantation bleeding?

I've been sleeping with this guy for a little while, and we've had unprotected sex quite a few times, but he's never ejaculated in me. We've always used the "pull out method", which I know isn't 100% effective. Well, 3 nights ago, we were having sex and I started bleeding. It wasn't a lot of blood, but enough to get on both of us. I put in a tampon just in case it leaked, but when I pulled it out, there was barely any blood on it. Then I was noticed blood when I wiped for the next few hours, but then it stopped. It was about a week or 2 too soon for my period, so I kinda freaked out. I mean, my period is a little irregular, but not THAT irregular. I've never had anything like this happen to me before. I'm in good health, and don't have STD's. I'm a 19 year old female. The only thing I could think of was ovulation bleeding or implantation bleeding. So I'm a bit worried. And I've been smoking and drinking since then, so now I'm also worried that if it was implantation bleeding that I'm ruining what ever is forming inside me. So please, somebody give me an answer...do you think it's ovulation bleeding or implantation bleeding or what else could it be?? Should I take a pregnancy test or go to a doctor or what? Thanks