I hope your concern is genuine.
First, recognize there is nothing wrong with being highly sexual. There is something wrong with being irresponsible, and there is something wrong about allowing your body to be used purely for a guy's sexual gratification, not the least of which is placing yourself at risk of serious disease.
I was a year or so older than you were before becoming sexually active, although, FWIW, by the time I was your age, I had "caught up with you" in terms of number of partners. BTW, I think the significance of your "number" is greatly overrated, although of course some people will judge you by it. Much more significant is the kind of relationship you have with your partners.
Having experienced something of the situation you describe, I'd cite a some things that worked for me. First, and I realize this is not something that will appeal to everyone, but I became active in a church. I was blessed that a non-judgmental older woman took me under wing and was supportive, even while knowing I failed to live up to the ideals of the church.
Second, make sure you have some sort of caring relationship with a guy before you become sexually involved. Doesn't mean undying love or that you're going to marry him, but you also don't want to be just his little f-toy. Make him do something other than getting a hard on to "get you"- and that you're doing it because you want to, not just because your partner does. Maybe look at it this way- you have to respect your own body before you can expect guys to. Doesn't mean you're going to be a nun- but do respect yourself.
One of the hardest things is to turn around a reputation. To do that you have to be consistent. Simple rules like "nothing intensely physical on a first date" or "no intercourse until you've know a guy a month" may help. I know, easier said than done, but you may need to do something to get rid of the "easy lay" rep (if indeed you have one). Sex can be part of a relationship, but it shouldn't be the totality of the relationship. A rule I developed in my teens- and pretty much adhered to- was that I wouldn't have sex with someone who I hadn't decided ahead of time was someone I'd be willing to do it with- the decision to do it shouldn't be made in the heat of arousal. Of course your rules need to be reasonable in terms of your own life, but if you fail to abide by one of your own rules, don't blame yourself or consider yourself a failure- just try to do differently in the future.
Third, consider finding a qualified therapist. If your sex life is limiting the rest of your life- or making you feel chronically unhappy about yourself- than you should try therapy. I cannot say that I've found therapy of great value in this regard, but many women- men too- have.
I hope this helps. I think there is no "one size fits all" solution. Recognize we all have sexual needs, some more than others. Don't berate yourself for your past- and don't feel you are condemned to keep living it.