Why wouldn't he respond?

I think you need to not contact him. I've made the same mistake and you just look desperate. I know how much it hurts, believe me. I'm going through it myself right now. Tomorrow will be 3 weeks since I found out my boyfriend was cheating on me and we broke up because of it. He told me he needed some space so I have tried to grant him that wish. As much as I know you're hurting you should try to go out with your friends and have the best time possible. Talk to your friends. Go to church. I work in a hospital and I just go in the chapel there everyday and talk to God about it. It helps. If you work on yourself and your own happiness who knows, he may see you later on down the road and then realize what he's been missing. Go out and buy yourself a cute outfit, get your hair cut, etc. I cut all my hair off and it was like a cleansing experience to do that. If you need any more advice just send me a message. I'm a super sensitive person and I have a hard time letting go of him. I know how you feel. Another thing you can do is go ahead and write that email but DO NOT SEND IT. Write him a letter but DO NOT SEND IT. Save it and read it later. You might be surprised what your wrote and you'll be glad you didn't send it.