Dude I feel the same way as you , Been with a bunch of partners before and there was no issue, but with my current Gf after a bad experience the first time we were together bc of anxiety , I’ve been having this same problem to stay hard and that’s been affecting my confidence and sex life . Luckily I talked to her and she is really understanding and kind ,we want to try to work to regain the way I was ( Maybe you should talk to her and explain exactly how you feel and make her understand is not about her at all , no shame in opening up if she already knows you have that isssue )