Welcome to BTG
I am noise intolerant and hate crowded places. Ear plugs are a good idea if you go anywhere noisy. I avoid crowded areas like the plague even going to the supermarket when I know it will be less packed and quieter.
On saying that, 3 months is very early in your recovery, so you need to be taking baby steps to avoid taking backward steps.
Anxiety is very common after a SAH. If that is really causing you a problem, it would be wise to see your GP and ask for counselling. As for the gym, take medical advice as to when it would be possible to return to that activity.