How do I get comfortable and less obsessive with the thought of a potential or existing partner sleeping with other people before me?

So, there’s an issue that’s been going on and I’ll try to explain it as clearly and shortly as possible.

Basically there’s a person I’m talking to and they started showing some interest in a more romantic way, nor irl but online.

My issue is I’m afraid to like them back once we actually see each other or meet up and the damn reason has been the death of me in the past and I struggle to deal with it the way I wish.
Basically I’m in my early 20s and a virgin with very minimal romantic experience. I as well have a set goal or mindset to not hurry that part as I don’t really have a need and I guess I’m scared to regret it I guess.

Anyway, this person is obviously like most people has more experience and that’s what I guess scares me. I wouldn’t say I’m jealous of their previous partners but I get scared or uncomfortable about it even if its literally normal to have that experience and it’s annoying me so much that my brain just cannot get comfortable with such thoughts. I don’t know whether I’m self conscious about myself and my lack of knowledge but its not like i can or want to change.

Even if its not for this person but in general for my future, I don’t wanna be uncomfortable about it or jealous and overthink absolutely everything when it comes to those things. Just like in my previous relationship I’d make up scenarios that would upset me for no damn reason.

I don’t really feel comfortable talking about this irl, especially my therapist buy I might need to eventually because it’s driving me insane how annoyed I am with my reactions when it comes to romance. I don’t wanna be a crazy obsessive partner but I do also wanna experience love.

So please is someone has been in a similar situation or has any advice or something to help me “fix” my problem please.

TL;DR To make it short, how do I get comfortable and less obsessive with the thought of a potential or existing partner sleeping with other people before me? Help. Thank you.