How do you let go of the love of your life when you don't want to and he doesn't want to move on but left you?

we had been together for over 15 month and were in love and he left me said he just didn't feel like being my bf right now were friends with benefits but still have felling for each other. it was his birthday to day and he wanted to spend it with me and no one else so we did im confused i don't want to loss him for good a my bf or whatever