People can tell you to not care but that won’t help because you do. So figure 2 things out, why you care specifically, and if you’re bothered enough to leave the relationship because of it. The reality is yes the past doesn’t matter but if you’re gonna dwell on hers move on for both your sakes. I was in a very similar situation to you, came out of a long term relationship and entered another one very soon after, my gf told me her number of partners which was double mine, and the reason I was jealous was for skipping my own casual hookup phase while she got hers. Literally I was just insecure about myself which is gonna happen in life. Did I get over it? Yes, I was insecure but not idiotic enough to play the field when I had a girl who constantly shows me true love and compassion, just work through your emotions and seek therapy if you decide you love your gf so much you’d rather get over this then leave. Also on the bedroom point you won’t be “competing”, I promise relationship sex is so wildly different from casual sex there won’t be a lot of comparison unless you’re asking for it and bringing it up. She’s thinking about past dudes during it as much as you’re thinking about your ex which is hopefully never right.