OP_ Have you never wondered if the 13 years of no sex in his previous marriage was not, errr, his "fault"? Blaming his ex wife seems very convenient.
An affair is not the answer- that would involve your emotions and another man's emmotions- unless you can find a fuck buddy who is happy to keep emotions out of it. You need to be honest- you are not just looking for sex, you are looking for affection and sex as an expression of love; an affair might give you that but it's playing a very dangerous game where lots of people could get hurt.
I went for sexual conselling when a boyfreind became impotent due to psycholgical reasons- guilt, fear of me becoming PG- he was very screwed up, and a virgin at 35.
The counselling/therapy didn't help make the situation better though the therapist gave advice- basically keep off the topic and let him "come to me" when he was ready. It did help me to move on though and leave that relationship, as I felt I had tried everything first.
In my situation, we slept in separate beds, and apart from hand holding and kissing, we had 3 years of celibacy after a whirlwind romance when he was very much up for it- 'scuse the pun.
In the end, I left him- even though I loved him- for another man. But we weren't married and didn't have children.
sounds to me as if your DH isn't facing up to it and maybe has deep seated issues which he is avoiding. If I were you, I 'd give him an ultimatum- seek help via his GPor couples' therapy- or you will leave. Harsh but maybe necessary.