I've been there and struggled with depression. You know what has been amazing for my mental health? Lifting weights and getting some movement in. Try taking a long walk and see if that helps clear your head. You're far from a failure, Op. Much love.
The weird thing about this sort of stuff is I believe genetics play a role. My father in law has worked in ag his whole life. Specifically spraying fertilizer and pesticides. He is obese and has a terrible diet. One would think he is riddle with cancer and died at 50. He retired at 67 and is overall somewhat healthy for someone who is 300 lbs. Life is weird.
Someone in a quarter zip with pants from 5.11 tactical talked to me at conference once. From then on I decided to burn all my poop, walk everywhere with a face mask, only communicate with smoke signals and only use cash.