How can I tell him its over without crushing him?

We've been married for 3 and a half years. He is in the military and is gone all the time, not from deployments but from different schools they are always sending him to. For the last 9 months I have been very unhappy. When he is home were barely talk to eachother and when he is away we fight. I've told him it needs to change and of course it never does. He has been away for three months and is supposed to come home in a couple weeks. I didnt want to tell him that i want a seperation while he was away but he told me he would rather know now then be surprised when he gets home. so i told him last week. He knows we've been having problems and even told me that he wasnt sure if he was still in love with me just a couple weeks ago. now that he knows how i feel he's now deeply in love with me and wants to do anything to save our marriage. and i feel bad but its just not something i want anymore. i love and care for him but more like a friend. he says he thinks there's a small glimer of hope (there's really not) so he's gonna keep trying to save us. i dont want that, i dont want counseling, i just want to go on with my life. and i dont know how to tell him this without hurting him. we have 2 kids together so i want to stay civil with him, i'm really not a mean person and i know this all sounds heartless but i'm really not. i dont know how to tell him.