I also had 2 years as a 'slut'. In fact, I even made a post about it on here about 7 years ago when I was asking whether it was acceptable to have slept with 14 people.
Now it's more than that but I'm 27 now and I've calmed down. But as I see it, as long as I fancied them and it was fun then it was fine! Some of them were actually really beautiful experiences and I wouldn't change them for anyone. Once I had sex with a German boy I met on the bank of a river in a small town after we had gone skinny dipping. And another German boy I stayed up all night talking to and fell asleep and realised I had missed my plane home. Some of them I still talk to on facebook. One of them ended up becoming my current boyfriend years later.
It is not ALWAYS about low self esteem. I had low self esteem until I was 17 and I became a 'slut' (inappropriate word!) aged 21. It was because I was very curious about everything in the world and wanted to do everything all at once and it was fun. There were a few because I was too drunk, but even those were fun in their own way. There was also a couple I deeply regretted and was very upset about and that made my skin crawl and me wonder what the **** i was doing. That's life.
Anyway. I don't think you can handle it and I think you need to think long and hard about why you find other people's sexuality disgusting. If your girlfriend HAS got low self esteem and you love her, why don't you want to help her be the best she can be? Why do you want to **** her up even further with your judgement?
I have had an argument recently with my boyfriend about someone he said he thought was attractive which spiraled into a stupid thing where I basically said he'd **** anyone and he doesn't execute much choice in who he's slept with. The real reason I said that? Because when we started seeing each other ages ago I found out he was sleeping with another girl at the same time, and then we were off/on for ages and he slept with her again in the 'off' bits, and I've decided she's not as pretty as me because she has dreadlocks and doesn't wear nice clothes. Is this all about my insecurity that he liked her as well as me at that time? Yes. Is this argument good for him? No. Am I dick for saying that to him? Yes. Does he have a right to sleep with who he likes? Yes of course. Am I going to apologise at some point? Yes, I need to do that tonight and work on not bringing it up again.
Do the best thing for her. And learn a bit about why you find it so disgusting, you may find it ends up causing you way less pain.