Dealing with the aftermath of losing a friend to suicide

Been really difficult recently. I lost my best friend to suicide a little under a year and a half ago. I feel guilty, like I caused it. I get flashbacks, memories, intrusive thoughts, of the situation and of him. Somedays they get so bad that I simply cannot sleep. He passed due to an overdose, and left a note to me saying that he always hoped I knew he was proud of me and that I was a great friend. I really never knew much about him, just that I loved him like a brother. I don’t remember what he was like honestly, it confuses me. I barely cry about it anymore, unless it’s one of the most difficult days. I overthink everything and plan for the worst, I’ve been paranoid for months. I’m constantly jumpy, concerned about everything. Recently just feeling like I have to be perfect, or else someone else will pass, or leave me. I don’t like my self image. I care more about peoples thoughts about me; than my own. I beg for acceptance from everyone and I’m trying to learn how to not care. I’ve been living with my sister for a few weeks, she’s one of my icons at this point, she’s learned to simply stop caring what others think and it’s helping me. There’s been times where I’ve met people and they simply say or talk a similar way to him and it makes me break down. I can’t concentrate on many things anymore. I don’t feel any interest in doing anything anymore, even major trips, seeing friends, being able to express myself. Overall, it’s been a very tough ride and I simply don’t think I will ever fully recover.