Are you alone or with your new GF?
You need to start breaking this vicious cycle, the sooner you start the better. Replace the negatives with something better, mindfulness or whatever, get out for a ride, do nice things for yourself.
You are not a failure for not wanting to socialize, or whatever else is stressing you out. We are all different and need different things.
As above, Gnusmas posted a helpline list so if you need to talk go to that thread.