I have severe depression, and I spent four years in a relationship with someone who also had severe depression. It's really hard, and it makes perfect sense that you're struggling with it. That doesn't make you a bad person.

Have you considered getting therapy for yourself? Even though you're not currently depressed, it sounds like you could really use the support. I found that really helpful when I was struggling to deal with the effects of my partner's depression. You can't change him or make him get treatment, but sometimes it helps to have a safe person who can listen to you vent and maybe give you some helpful perspectives. You deserve support too!