Long distance relationship & he cheated only after 4 months!

I live in Europe. I just found out that my bf in the Middle East cheated on me with his ex. We just had a lovely vacation there and a week after I got home he tells me, he slept with her. I got suspicious because of her comments on fb, so i kept on asking him. He told me he needs some time to think about our relationship. So a few days after he tells me that he cheated. I asked her, she says they are back together and just got back from a get away trip. He admits that.....
My heart is broken, I can,t sleep, I can,t eat, I can,t breathe. He,s begging me to forgive him. But I know one thing, I will never be with him again.