You say you started a few months ago; I take it you started remote and you've been remote the whole time?
I started my current job in quarantine and I've dealt with a ton of impostor syndrome ever since (I'd never really had impostor syndrome before this). I'm constantly feeling like a disappointment, wondering if they still want me, trying desperately to come up with ways to prove my worth.
I think at least part of that feeling of inadequacy is based in the lack of day to day, nonverbal feedback and interaction with my coworkers and managers. I feel precarious because I have very little data to go off of one way or the other. We even do one-on-ones, but still. A conversation about my performance once a month doesn't replace daily body-language, off the cuff remarks, expressions on people's faces after I've made suggestions or completed tasks.
Anyway: I'm hoping my situation will get better once I'm back in an office. Maybe yours will too.
Best of luck.