Hello! I'm sorry to hear that. Understand the basic thing. It'll take time. It will really take time, and yet there will a possibility that you couldn't move on. The thing is, give yourself time. Even I'm going through the same phase. I know, it sucks big time, but believe me this is the best way you can relieve yourself and your heart. And idk if I should say this or not, but as you mentioned, he wants to be alone, I'll suggest you to give him time. Everything's gonna be alright.
gracelana696