I feel like my relationship is getting worse, I need yours opinion or insights

TLDR: I am starting to feel problems in our relationship and feeling like I am in one sided relationship because of mental struggles of my partner and my own. I need an insight of someone else because I don't know if I am being the bad person or if I am not. I really need someone's opinion.

Me and my partner have been dating for almost two years now. Everything has been going great. We slowly learnt so much about each other to the point where we can't help but laugh after finding yet another thing that we have in common. There is way more we have in common than not.

Or so I thought. Everything has been going so amazingly. Of course you have ups and downs as in any relationship but this has been the most healthy relationship I have ever been in.

I need to mention that even if we met in real life he had to move so we see eachother usually only once per week.

The problem is that we both do have mental health issues that until now hasn't ever affected our relationship. Lately my partner started to have way more difficult time and I am trying my absolute best to be there for him 24/7 even if we can only call or chat.

I know mental health struggles are one of the most difficult ones of them all. And I am trying everything I can to help him. But I can slowly start to see his problems affecting me too. I worry about him all the time. We rarely text. We sometimes text only once a day, which for long distance isn't really suitable. We don't even call anymore. I noticed I started to put my own problems and feelings aside because his seem so huge to the point where I don't even think my have time and space to be talked about.

The problem: I am starting to feel like I am not even in relationship anymore. I know it might sound harsh. but whenever I brought up that he never answers me or texts me (never do I get explanation why) he says he will fix it but he doesn't. It feels like empty promises and apologies that never mean anything.