Is partial disability benefits for people with health issues that make them miss /some work/?

I have idiopathic epilepsy, which basically means I have small seizures very frequently and larger seizures periodically. My boss does not allow me to miss work when I have a big seizure, telling me I'm using it as a crutch when in fact I'm not even legally supposed to be driving to and from work, or for work, because I've passed out in the past 6 months. I have tried searching for partial disability, because I do NOT need full benefits, just enough so that when I'm unable to come into work I'll still be able to pay my bills (last time I tried to leave early - around 2PM - because of a seizure I almost lost my job - don't tell me it's illegal, the circumstances are difficult). The BIG problem is that I get paid cash, so I can't prove that I have a job? Ifigure this means I can't do anything but I can't find answers online. Please help if you can :)