Yeah, posting is SUPER scary and anxiety-inducing (and frankly, flat-out embarrassing some days). You are not alone.
But I'm really encouraged that there's a lot of good support in this thread here for dealing with that kind of anxiety. I think the key to feeling healthier about your contributions is having a growth mindset and making sure that this is what you want to be doing. I get it. I always have the most fun while I'm writing or drawing. Making stories is almost like a coping mechanism for me (for just dealing with life in general). For as long as I can remember, I've always been crafting a story/script/etc- and if I'm not, I feel empty/joyless. But I used to keep those stories close to the vest and share them with only a few people because it's safer that way. But I'm glad I made the switch and started producing for mass consumption. It was scary as hell (and a little disappointing too) when I first posted my comic- and yes, right afterward, all the anxiety flooded in- but it's been completely worth it for the growth I've experienced as an artist (with more yet to come, hopefully).
At the end of the day, I'm doing this because I love it. And once you put your mind on growing and learning to make peace with who you are and what you make, hopefully you'll feel better.
Even what you just did, posting here about your anxiety, is such a great thing. Because you're not alone. And not only do you know that now, but we're all reminded that we're not alone too. Because you reminded us we're not alone by putting a mirror to our own struggles- and that's such a powerful thing.
And when someone reads your work and feels like they're not alone because of your art, that's such a great thing. And you may never get that feedback during that moment (but I hope you do).
Finally, I don't know of a single artist that I respect who hasn't mentioned their imposter syndrome. Even the greats can feel like they're not that good. And honestly, that's one of the reasons they're great. We get it. We learn to love our own little peccadilloes. We find our our strengths and we play to them. We grow.
You do you. I can't wait to see how you blossom.