My Boyfriend Left Me and I Don't Know Why

So, my boyfriend left me on Saturday. We were together almost 12 months. The first 8 months were absolutely perfect. He was sweet and loving and we were vest friends. But he is a recovering addict and about 3 months ago, he got a job being around people who were very open about drinking and drugs. He changed almost overnight. He started staying out all the time, not coming home and not answering my messages. I didn't know if he was alive or dead, then he would come home a day or so later like nothing happened. He saw that I was upset about this and it started getting awkward because he never wanted to actually talk about anything. On Tuesday, I asked him while I was crying if he still loved me because it just doesn't seem like he wants anything to do with me lately. He told me that his feelings for me have not changed and he would try to do better. But Saturday, while I was at work, he packed his stuff and moved out. He broke up with me in a message and said it was for the best. He deleted me and I haven't seen him since a day before he left. We went from best friends to strangers and I don't know why. Everyone is saying that it seems like he got back into drugs. But all I know is I feel so ugly and worthless and unloved. I am devastated and so alone, and with my anxiety, this is terrifying. I don't know what to do.