I hope it’s a good thing I sound like oyur therapist 😀
I really understand how you’re feeling. I’m starting out as a comedian and last week I rocked a hall full of people with laughter… after I had spend the whole morning crying and unable to go to work.

Are judging yourself right now? There is a lot of “I should” between your lines.
“This irrationality of my mind is so frustrating.”
Could this be your inner critic speaking? The part of you that says “Stop this now you stupid idiot or you will ruin everything!” (Belief: You are not allowed to make mistakes. You are not good enough.)

One thing I forgot in my list was: Write down every single memory of a moment where you felt those painful feelings for the first time.

Your experiences are really hard, but they are in the past. Your body and your mind need a lot of work and time to understand this, so be patient with them!
You can be really proud that you are in a relationship after all after this shit, and that you are facing all that pain and fear! Congratulations! 🙂