With a combination of social anxiety and depression meds it is surprising that you did not go for any kind of therapies. Especially CBT, you need cognitive behavioural therapy to counter your anxiety. Mostly these conditions occur with long term thought patterns formed since very young age. So for example: you might be afraid to perform solo on stage or in front of a crowd due to fear.. of rejection or raised heartbeat, sweaty palms, self-doubt etc...could be due to lack of appreciation... Many a times we associate too much emotions to the outcome i.e. success on which we may not have control but we do not enjoy the process of preparation, learning and knowledge...hence we stress a lot thus increasing the chance of failure. Another aspect is self-confidence, have you noticed when we know something in and out we are more confident but when our know how is less it's quite likely to feel uncertain and we start questioning ourselves.
Next Steps
consult a CBT expert or you could consult here as well. your medication shall be more effective when you undergo counselling therapy.
Health Tips
in the mean time, take baby steps towards social anxiety. take a particular anxiety situation, try to write down what exactly you feel just before that moment. what symptoms you experience, after the symptoms what crosses your mind, which thoughts come...try to find from your previous experience if there was a single incident when you did not feel the same. so use it to counter the feelings and thoughts of your anxiety situation.
practice deep breathing it helps a lot to calm down the nerves during anxiety. all the best for your preps and you know where to reach out for further help.