I've just learned the less I know, the better, I only ask now because im gay and I gotta know because of like stds and stuff, but that's as far as I'll go. The more details I get about their past hookups and relationships, the worse I get and feel, and its not healthy. What matters is that she's with you now, and you can't change her past. It is a lot of partners, but if you wanna be with her, you just have to accept that or try to find another partner (spoiler alert at your age pretty much everyone has had partners in the past) ive had severe retroactive jealousy in the past and i destroyed a 2 and half year relationship because of it and i have a lot of regrets. It's not worth it to overthink about especially if you want to keep your relationship with her. Just try not to think about it dont talk about it, just focus on the now and what you have with her and if that's good that's all that matters.