Help getting a job with selective mutism

Hi, I'm 21 and have never had a job because my selective mutism has stopped me from being able to communicate and I get bad anxiety outisde the house, therefore it's hard to do interviews or anything.
I've basically got no GCSE's either and my dad is threatening to throw me. basically i just need some advice on what to do

I do not have SM, but I have a suggestion. I am a web developer and I work from home. Most of my communication with co-workers is via email and Skype chat. Very little is verbal.
You might look into taking some online courses to get a certificate in web development. Then you could apply for a "remote" junior web developer position (there are plenty). Let them know in your cover letter that you have SM which limits your ability to communicate verbally, but you can communicate effectively via email and chat. Maybe they will allow you to interview in a written format.

By the way, I am not suggesting that you completely accept the mutism and never push yourself to improve. But something like this could be a stepping stone into a career. Then once you have worked with a small team of people for a while you may become comfortable talking with them on the phone.
Also, if web development doesn't interest you, there are lots of other "remote" jobs out there to look into.