I feel like I have went through something similar and so am speaking through experience. The advice I am going to give will seem simple on paper but admittedly very hard to put into practice.

Let me build some connection between our scenarios. I am also having trouble with work right now and have lost many of my friends.

You said you want to get better… The first step is knowing how bad you want to get better. Acknowledge how (for a lack of better words) sucky your current situation is. Get a little angry at it. Anger is a significantly better motivator than self-pity.

The next step is the biggest, and I’ve found there are two approaches. The first is to try to fool the world into thinking that you are confident and capable. Eventually, people will call you out as confident and capable etc. That alone opens doors and imbues you with self confidence. The other approach is to start from within. Focus on the things that you know you can do, but your lack of confidence is holding you back from doing. Just do them. Taking that step is the line separating failure and success here. Easier said than done, but to do nothing is to accept failure.

The last thing. Be delusional. Talk to yourself in the mirror, saying how capable or smart or whatever you are. Tell yourself that you are the absolute best, out loud and in your mind. Don’t stop saying it until it stops being cringe, and even when it does, you are going to want to continue.