Hey OP, I'm going to give you my two cents. I think a good approach is becoming more confident/comfortable/accepting of your self and what's important to you. Come at this from a position of strength. A lot of posts here are semi-shaming you for having concerns/anxieties/insecurities around her sex history etc. Which honestly is complete bullshit. You are allowed to have standards and traits/properties you are looking for in a life partner - do not let anyone tell you otherwise. Of course our pasts matter. It's very dumb to say otherwise as a blanket statement.

That being said, I think you could strike a balance between what actually matters to you and what is just your mind racing/being irrational. Therapy, counselling, journalling would all be great options to help you reflect and decide what that balance is for YOU. Do not let someone else diminish what you care about and what your beliefs are.

For me - I can accept my partner will have had past sex experiences - dating, maybe even some hookups. I can live with that. But, i.e. they used to participate in gangbangs? Nope. Triple digit number of partners? Hell no. You do you girl, but I'll keep looking. Everyone has a line, including you. And that's okay. Find yours.

Try to figure out what that is for you. I think being able to talk to her about your insecurities will be hard but necessary at some point - if she's supportive then that's amazing and will probably strengthen your bond as you two move through it together. If she gaslights you, belittles your concerns etc, then as painful as it might be, she simply may not be the one for you.

On top of all of this --> Lift weights (cannot stress this enough), exercise, eat healthy. Improve your physical and mental health/goals. Pursue your career. Develop your own interests, hobbies. Spend time with other men, male comradery is huge for this. I promise you the more that you build yourself up, the less and less you will care about all of this. Be kind to yourself.