24F, ADHD, OCD - off meds, T1D

Loooooong story short I left my anxious cat in a cattery and he didn't eat or sleep or pee for 2 and a half days. This gave me panic attacks before leaving him there, while he was there and even after I brought him back home. Physically he's okay, he started eating. But he's been meowing continuously and sometimes yowls and refuses to play. His loudest tantrums are between 3am-8am non stop, and it's driving me insane. His pain and my guilt. I feel like I will never get him back to normal. That I made the biggest mistake of my life and lost my kitty to trauma. 
He is my whole life. Everybody keeps saying that he'll be okay but how do i believe them when he's so visibly not okay? I feel lonely and I'm crying as I type this and I want my cat to be normal again. I'm hurting my poor parents who don't deserve this. They deserve someone who's better, healthier. 

Worst of all I'm blaming myself. I wish I never adopted him. I love him unconditionally but I'm not strong enough for this unconditional love. I can't give him up, if something happens to him I WILL kill myself. I'm scared something's already happened to him. 

I'm crying in my office. I feel so lonely.