Help....i feel like my marriage is spiraling out of control

We have been going through a rough time...since April. It started when my husband said he feels depressed, and has poor memory...doctor's visit and testing later, dx with sleep apnea/disturbance. Got a cpap, also started on Wellbutrin for mood and HCTZ for high blood pressure. Well he still feels like crap

The problem is, it's wearing on him, me, and our young kids. I love him and want him to get better, and told him he needs to take care of him to be a better husband, father, and vet at work (that's a whole nother issue, high stress job).

He knows he should be doing everything the doctor tells him, and doesn't, and doesn't feel better. So i tell him to go back to the doctor, and he won't bc he knows he needs to try harder. I can only be sympathetic for so long, I don't do well with those that don't help themselves. I have also suggested counseling to help him manage his stress ,and he quotes some bullshit from the departed about being impervious to psychoanalysis.

He also keeps telling me he feels like he's screaming inside, like he's not the same person he was 6 years ago (still in grad school, no kids yet), and he keeps having nightmares about me leaving him. I feel like he's headed for a mental breakdown and would like to prevent that before it happens

HELP!