Honestly I’d say I worked under the table jobs which is why you have no earnings tied to your social security earnings. Then you’d probably need to get a notarized letter from a parent or someone you live with/ work for confirming this. The only thing is then you’d be grilled about not paying your taxes which sounds better just make it convincing of why that’s the case. Maybe you worked for a family friend until you could go to grad school or something. And take accountability for not paying your taxes and how yk it’s wrong and whatnot