Is Citalopram causing these problems?

My boyfriend of almost over 2 years became depressed in October 2017, he continued to tell me he loved me and stuff and it was all cause by him having extremely poor friends who would make him anxious and lonely. He finally got the courage to go to the doctor in March 2018 and the doctor prescribed him citalopram and everything was okay, he got his dose upped from 10mg to 20mg and everything seemed okay but then he suddenly starting getting really bad side effects like severe paranoia and vivid nightmares of people he loves dying due to him. He started telling me he wasn’t good enough for me and never was and I reassured him he was amazing. Then out of the blue last week he just dumped me with no reason, he said he doesn’t know what he’s doing anymore and he’s not himself and doesn’t like it. He still messages me and tells me he still loves me but can’t be with me because he can’t cope with anything and is very paranoid. He wants to change his pills due to how bad they have made him. Are the pills causing these problems or is he just thinking that they are? I don’t really know who to ask and a doctor seems like the best option as they are trained and know what is going on

Age: 20
Female
Medications: None