He could be depressed and aware of it but unable to stop how he feels. This is probably why he's more interested in venting to you about his issues than having to hear about any of yours. Has he been exhibiting any of these traits?:
What are the symptoms of depression? Difficulty concentrating, remembering details, and making decisions
Fatigue and decreased energy
Feelings of sadness or unhappiness
Irritability or frustration, even over small matters
Loss of interest or pleasure in normal
Feeling hopeless, irritable, anxious, or guilty
Loss of interest in favorite activities
I think at this point if you realize that something is definitely wrong, (obviously he hasn't always been this way) to the point that even his buddies worry, then you shouldn't beating yourself up about it as though you are a victim. He's having issues that's making him act this way, this your time to really shine as his wife and stick by him during this difficult time. Consider speaking with a couples therapist available on this site.
therapists online Maybe they can give you more insight as to what is going on. It's only $25 bucks for about a 10-15 minute session. It's best to at least know whats going on through a professional than wondering and crying to yourself.