Heart break

My bf of a year and a half randomly broke up with me 2 weeks ago while I was on holiday. It was so out of the blue I wasn’t expecting it at all. The night before he went out drinking with friends and completely ghosted me for 12 hours. Something he had never done before. He was usually really good at checking in while out. The next day we had a fight and he told me he didn’t want to be with me anymore. I later found out he was also on acid that night. He rarely used to drink and now all he does is party and do hard drugs. It’s like he completely changed over night, He was a perfect boyfriend and honestly i probably didn’t deserve him but now he’s someone I don’t know and I don’t like the new him. He keeps telling me he wants to stay friends but is constantly switching up. One second we’re cool and talking and the next he’s treating me like complete shit. I have never been treated worse by anyone than I have by him in the last 2 weeks, This new version of him is a horrible person. He never even gave me a real reason about why he ended it, he said it was because I deserved better but that’s what people say when they don’t want to hurt someone’s feelings. He was also telling me he loved me and couldn’t wait until I got back the day before we broke up but then told me 2 days later he had already lost all feelings for me. I just don’t get how he completely changed literally over night. It hurts so much, we were each others first everything’s. We went through high school together, graduated together and got experienced being adults working full time jobs together. I feel so hurt and lost. The worse thing is thinking about him moving on with someone else. It literally kills me inside. I keep blaming myself thinking if maybe I did this or didn’t do this he would still love me. I miss who he was 2 weeks ago so much. He used to be someone to brag about now all he does is hurt me.