How do I get my husband to understand that I need him to be a better provider financially?

I have often worked two jobs and now I have returned back to school! I don't know if I can say I'm the sole support for my family but I am the most consistent with a bi-monthly salary and benefits that my family can depend on. The problem, my income still isn't enough to cover the bills and my husbands income from his business venture (self-employed) is inconsistent and never enough. His job is really seasonal (he builds Harley Davidsons and works on them); he often barters and trades for things we need. He's always saying, let me see what I can come up with! But when raising a family, it's not what you "can come up with" but you gotta have stability and be predictable. Yes, he's come through alot of times, but the stress it puts me under sometimes is unbearable. I've asked him to get a regular job and he says, NO! He says he's not healthy enough and sometimes I think he's afraid because when he was 20 years old he got a criminal record. But there is something out there for everybody, you just gotta try! He's a wonderful father with the exception of bringing home the bacon and I cant see leaving and putting my youngest daughter and son through a breakup! We raised 3 adult children already and I can see in my boys where they don't have the initiative either to work! My adult daughter is like me when it comes to working. Im tired of bringing home the bacon alone and wearing the pants financially in the family! I need a break and all I want is for my husband to share the load! HELP!!!!!