As far as I know, nobody has yet invented medications that keep negative thoughts "at bay." I was on Lexapro in the past and I didn't find it helpful for either depression or anxiety. I don't know of any other antidepressants that would give the effect you're looking for. (I've been on many.)

For thousands of years people have found that alcohol can reduce social anxiety, while you are drinking it. But it doesn't prevent self-recrimination afterwards. Benzodiazepines can work similarly.

I had pretty severe social anxiety growing up. The best treatment, IMO, is to deliberately "socialize" yourself. That means desensitizing yourself by repeatedly exposing yourself to social situations. That's what I did. It can seem like a slow process, but, with experience, you get more socially competent.

Another help, I believe, is to challenge your own thinking. So, after feeling I interacted in a way that might have come across badly, I've asked myself what real harm did I cause anyone. Also, I tell myself that I have a right to make mistakes.

I think you kind of need to talk yourself through these episodes of feeling bad about your public performances.