After 3 years of marriage I've gone off sex..help!

[Unregistered]

I am a 38 years old, and I have been married to my lovely husband, who is 35 years old, for 4 years. This is my first marriage. When we first met, sex was great, but for the last year I just don't want sex with him anymore. I'm not looking for an affair, as I love my husband very much, and I would never want to hurt him. I enjoy his company, being with him, and everything we do together...but when it comes to sex, it just isn't happening for me. My husband is in the Army, and does have to spend time away from me...up to 6 months at a time. He is currently serving in Afghanistan, and is due home in 3 weeks. I am looking forward to him coming home very much, but I am dreading the sex side of things. I am really starting to worry about this. He was previously married, and his ex wife cheated on him whilst he was out serving in Iraq, which lead to the separation and divorce . I don't know why I don't want sex with him anymore, and I wish I did. I don't know if this has anything to do with my past, and I am worried that it does. My mother re-married when I was young, and when I turned 13 we moved to a different country. I didn't get on with my step-father, and I found I was fending for myself from a young age, as my mother was very wrapped up in her new life. I got mixed up with the wrong people and found myself involved in prostitution at the age of 18. This did continue for some years, and I am now worried that this has had a permanent effect on me. I have had previous relationships, but none have lasted longer that 5 years. Please, can anyone offer any help or advice, as I have nobody I can talk to about this and I feel it's starting to ruin my life.