I have mild social anxiety. Until I was able to see an NHS counsellor, I spoke to The Samaritans who just listened. Sometimes it's healing just to get your feelings out. I found the Samaritans did this brilliantly.116 123 24 hours a day But a counsellor will help you with strategies to improve your social interactions. I also found the Elefriends forum from Mind helpful too. Elefriends.org.uk
I am in London and waited 8 months to see a counsellor. Different areas have different waiting lists. In your area it might be shorter.
I had depression two years ago. I am still anxious and find it hard to ask people for help, for example, to make eye contact, and I don't like going out with anyone but my husband and daughter. I know what it's like to have low self esteem and self worth. It's horrible.
Your focus needs to be smaller, however. The goal is to have a girlfriend and more success. You need to take baby steps towards this. For example, you need to go out and do something that puts you in contact with other people. Before the lockdown, I accepted an invitation to the pub with a colleague instead of turning it down. It was awful, but I did it. Build links with people at work and in your community. Even if it's only saying hello to the postman.
You also need to find your "tribe". What are your interests? For example, can you play tennis? Do you like books? Is Animal Crossing your vibe? Do you appreciate wine? Look online for quieter events like a book signing for example, and try and interact with one person. It might work out, it might not, but it's a step. If you feel rejected, it's totally a normal feeling. It's hard to move on from rejection if you are anxious. But if you can replace the negative feeling with a positive one, it helps. (I don't think I made a good impression, but at least we agreed on [...]). If an interaction goes well, it boosts your confidence a tiny bit. So then try and talk to another person and build it up.
I'm not saying you will get over these feelings completely but there are ways to cope. Cognitive behavioral therapy might help. Your local CMHT might offer CBT as an online course.
I also agree with pp and ask to find out if you are on the autism spectrum. So many people are walking around on earth without realising they are autistic.
Are your parents supportive? Do you gave any siblings who can help you?