Get a lawyer. A lawyer helping you get SSDI/SSI will always be working on a contingency basis. It's illegal for them to do otherwise.

If you have a hard time getting a lawyer to take your case, then you don't have much of a chance.

If you have a history of working successfully, that will weaken your case. Being young weakens your case. You might have to rack up more job failures to be seen as really having lost your capacity to work.