How can i help him?!?

Please help! I’m currently in a “situationship” with this guy. It’s been about a year. “We’ve known each other 20+ years, since elementary school. This past year, we just started getting to know each other on a deeper level. Anyways, he does this thing where about every 3 months of an amazing period, he tells me how he doesn’t feel like he’s good enough for me. He will ruin my life and etc etc. i don’t judge him for anything that has happened especially before me but he won’t let that go. I know he’s using that as a shield to push me away but idk what to do. I love him and he loves me but I feel horrible some times bc idk how to make him know that i do not feel that way. We talk about it a lot. He’s my best friend. He’s a kind, hardworking man and an amazing father (from a previous relationship). He makes me so happy and it’s nothing but love when we are together. However, i can’t seem to find the right way to let him know that he’s more than enough for me. He deals with depression and was recently committed for threatening suicide a few weeks ago. 😢😢 I know he has to deal with a ton of things from his entire family depending on him to support them because he makes good money, to his rocky relationship with the mother of his child, and everything in between. I just want him to know that I’m there and that hes not alone.. Although Neither of us are quite ready for a relationship right now, our feelings got involved very fast and we’ve been inseparable every since. It just stresses me out that when he gets like that, there’s nothing i can say to fix it without overstepping those “boundaries”. He crawls into his hole and comes out in a day or 2 like nothing happened. Is there something else that i should be doing or should i just leave him alone and allow him to cope as he sees fit? I feel so helpless like there’s nothing i can do to put him in a better space and realize that he’s amazing.