Bf wants to break up

Hey everyone! I have been with my bf 6 months , 2 months ago we moved in together. Lately I have been very jealous and insecure because of social media and we fought more than we should have. 21. December he went to Germany to visit his cousin. On 23. December I got a message on Instagram from fake profile saying my bf is with another girl. I didn't believe that person and didn't wanna confront my bf about it because I thought it would look like I don't trust him. Instead I made a fake Instagram account and followed his friends to know what he is up to. He found out and got mad, said he hates me and that he doesn't give a shit about me anymore. He said we are breaking up. Since then he has been ignoring my calls and messages. I messaged his cousin that he is currently staying with and asked him can he help me. He said he tried talking to my bf and that my bf looks serious about ending our relationship. He also said my bf is very angry and that I should stop contacting him completely. His cousin said he will try to talk to him every day to help me save our relationship. And that he will update me on what my bf thinks. I am so scared to lose him. He is coming home 30. December and I'm afraid that as soon as he comes back he will end it without even trying to fix it. I am willing to change and be a better gf to him. What should I do?