My husband is having a lot of problems and I don't know how to help?

I think your right when your seeing signs of depression. You are also probably right when you say your too close to him to really figure it out. Your looking at all the possible causes in terms of his past as you know it. Odds are that it is something closer to home and much more recent that is responsible for his problems. If he continues to with draw you may loose him completely. I think you need to figure out at what point forcing him to see a psychiatrist is reasonable. If you don't do it then you will eventually regret it.