I wanna possess my girlfriend's sexuality

Hi everyone,

In every relationship I have been, I realized I wanted to know everything about what my girlfriend was doing with her body. This is a terrible feeling, and I strive so hard to keep me far from those thoughts, but it keeps coming back. I can feel that it is part of being unsafe, I feel like she would/could replace me by doing it by herself, not because she don't want me but bc obviously she knows herself better than me and can give herself more pleasure alone. I feel like I'm not that wanted and not as a sex necessity. In fact all of it is fear bc she doesn't make me feel like that, but here it is, thinking that she has more fun alone than with me or even than me alone makes me jealous or something like that. The fact is that I would love her to give her sexuality to me. But I fighting against it !!
If anyone went through possessiveness trouble, just tell me how you stopped thinking that she/he would let you down because she is doing it fine herself. I already spoke with her about it and she told me what is right on the "ps" underneath

ps: I am in total consciousness that these thoughts are bulls***, I mean this is absurd, she loves me and this is different by my side than alone, but here we are I can't help.

Thank you