I know that title looks bad, but my (18M) gf (17F) has never cheated on me and I truely don’t believe she ever will, but I have bad anxiety and I just rly overthink things and always feel like she is cheating on me whenever she’s at parties, or talking about other guys when I’m not around. Another part of it is she’s slept with 3 other guys and she was my first time

How can I stop overthinking and obsessing?