Hi Anonymous (1st post),
I know exactly how you feel. yes it hurts like crazy but it probably isn't your fault.
Our sex life was fantastic up until 2 years ago when it started to go down hill and there would be months in between. The last time my husband slept with me was 8 months ago. Stress is the biggest cause of low sex drive and erectile dysfunction. If he cannot get an erection, then he may feel like a failure and embarrassed. As far as cheating goes, I doubt it very much. You would know 100%, trust me. Try avoiding sex for a while, de-stress together with kissing and cuddling and no pressure. That was the advice the marriage counsellor gave us and we are trying it.