Assalamu Alaikum - I'm Struggling With Pain and Grief

Assalamu Alaikum brothers, I've been getting really bitter lately. My life has been tough for the past four years. I'm in my mid‑20s, male, unmarried. I feel like I might have some kind of mental health issue. I just can't seem to be happy or enjoy things. I keep focusing on what I've lost or what I don't have, and it drives me crazy - sleepless nights and all. I know with certainty that Islam is true. I've read a lot and checked the primary sources. I know my purpose is to know, love, and worship Allah and to try to please Him as best I can. Still, I get thoughts like “Allah doesn't love or care about me” or that some things will never be mine and I can never get what I want. I understand these are whispers of Shaytan, but in those moments I feel paralyzed. I've been struggling with my self‑image. When I'm bitter to someone I feel extreme guilt because I don't want to hurt anyone. Sometimes I even get frequent thoughts like maybe everything would be better if I just died. Yesterday I couldn't do anything the whole day - I was stuck in bed. I don't really have any coping mechanisms right now, healthy or otherwise. Mostly negative self‑talk, daydreaming, and sleeping as long as I can. I want to say Astaghfirullah more, do more Dhikr, pray more, but I can't seem to make myself get up. What should I do?