I'm sorry you are having a tough time. It just seems like the new relationship plays into it somehow. Get rid of his stuff, messages, etc as quickly as you can. Do you have to cross paths with him? Time does heal a lot. I know that doesn't sound good right now but it does. Keep yourself busy and distracted from thoughts of him. When thoughts come...let them. They will eventually dissipate. You know how they say don't think of a pink elephant. Same here. Best wishes on healing.