Help! Depression/suicidal

My husband of 5 years for the past 3-4 weeks has had a major change in attitude. It started first I noticed with him losing interest in his hobbies. He didn't want to do nothing. He was very prideful in little things like cutting the lawn to just working around the house and such, then all the sudden I find myself doing all the things he'd usually do. He spent a lot of his free time playing pc games, and now he doesn't even want to do that. He started waking up randomly at night almost in what seemed like panic attacks and Monday, he wanted to just up and quit his job because he says he is miserable. When I explained to him that we would lose a lot of he just quit, he didn't seem to care an just told me he couldn't go back he was depressed and that if he had to go back he felt like he wanted to drive his truck over a mountain. He's done this time to time. He's quit a lot of jobs hes had but this one he's had for years an just out of no where he went back to making these impulse decisions. I don't know what to do, how to help really. Hes 25, he lost the only person he had, (besides me) his mom last year followed by we lost a baby in January and are now suffering from infertility. I think the weight of everything is just crushing him but even when I offer to get him help, he refuses. When he was a teenager, he was a drug addict, spent 3 years in prison for burglary. He got out and I met him 2 years after he got out. He built himself up and now we have a new home, new life and he seems to be going back downhill. I love this man with all my heart but how do I help? If he refuses anything I offer, doctors, meds, therapy. He has no interest in helping himself and I don't know what to do.