Should I leave my depressed partner?

My bf and I have a lot of history but have been together for 2 1/2 years. For the last 6 months, we’ve been in a long distance relationship. We’ve had alot of issues due to our attitudes clashing.

In the last 6 months he’s changed dramatically .. recently he has opened up and told me he feels he isn’t well mentally. He feels like he’s destined to be alone, he loves me with all his heart but feels like he can’t love me the way I need to be loved. He doesn’t want to break up with me but he feels like its best for him to be alone. He’s tired of putting a front for people. He’s really adamant that he does love me but he doesn’t want to hurt me. He told me he thinks I should just let him be.

I’ve been chalking it up to he’s been going thru a deep depression. I refuse to leave him. We’ve loved each other since we were 14. In my darkest times, he was there for me. I can’t bring myself to leave him but he told me he doesn’t want to be in a relationship .. he doesn’t feel like he can be functional in one right now but he doesnt want to break up with me. As confusing & heartbreaking this has been, I want to be by his side. He’s the one who keeps telling me I shouldnt since I’m such a good gf, he feels I deserve better & someone who can make me happy.

Should I follow my instinct & stick by his side or respect how he feels?