Idk if I have imposter syndrome or nah, but I've definitely related to some of the signs.

What helped me is 1) I had a few managers (fortunately) who did not shy away from telling me when I did do well. 2) choosing to believe (gets easier over time) when they gave me feedback, both the bad and the good. And 3) noticing that alot of ppl around me really weren't up to the standards I had thought a position like theirs deserved.

It also helped that I have multiple projects that have run successfully, and even projects that my managers thought deserved to be submitted for awards, which costs money to the company to do so, so they wouldn't do it just to make me feel good.