I am skimming as work is kicking my ass today, but I totally get the imposter syndrome. I was underappreciated, underpaid and just generally trodden on for years at my old job, and I still can't quite believe the position I have found myself in a year after finally leaving.
It takes time to build confidence I think, and even then, we tend to doubt ourselves. I'm trying very hard to remind myself that I am good at my job and I deserve this, and I know you all are/do too.
RLF always says, if you're not being pulled in for a bollocking, then you're doing just fine.