First of all you need to seriously SLLLOOOWW down your "love life". As others have said lust and love are not the same thing. You really should take a look at why you've had so many partners in such a small amount of time. Not just because of the reputation that can get you but mostly for your health! And not just your physical health (although that is a serious issue) but also your mental health. Eventually this behavior will start to hurt you. Heck it already is it sounds.
Now as for this guy. My first instinct is to say he's a jerk for judging you based off your past. But then my second thought is... well part of me can't blame him. Please don't take that wrong. I am sure you are being honest that you'd never cheat on him or hurt him or anything. But put yourself in his shoes. Say there was a guy you liked and you found out he'd had a ton of partners in a short amount of time. Wouldn't you be a bit worried? Most women would. Most women would think that that shows a bit of a lack of respect for sex, women, and monogomy. They'd also be worried about STDs.
My point is that he has a right to be a little taken aback and hesitant about getting into a relationship with you after learning about this. This does NOT mean you are a **** or anything. It just means that what you do in life will reflect on you as a person. And while it may be in the past and you have changed people are going to judge you by these things no matter how unfair that may sound.
So what should you do? Talk to him. Tell him how you feel and how you have changed. Ask him if he'd be willing to give you a second chance to proove you are faithful. But also respect the fact that he might not be comfortable with this right now. And if so then let him be. Maybe after some time he'll see that you have changed.
Good luck and I hope you didn't take any offense with my post. I was by NO means trying to insult you. We all do things in life that paint us in a light that might not be who we really are. So I am by NO means judging you.