Give him your phone and tell him to break it, symbolically. You can get a new one. Or just throw away your SIM card from your phone. Do it in front of him as a way to prove how much he really means to you and that you would make any sacrifice.
I don't know if trust can be fixed. Sometimes it can and other times it cannot. Give it a shot by talking to him and get a feeling on how things are going.
Good luck.