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A sex therapist specialist (not a generalist) may be quite helpful in this situation.
After all, the pain is an issue that he is dealing with and it sounds that he has a healthy libido.
You could point out to him that you are not per se complaining but rather pointing out some information that you would like him to address. A qualified sex therapist deals with situations like this and would be able to assist you both without the need for feeling embarrassed. It is a natural response on his part and he probably feels anxious thinking that you are upset. Of course, as you continue to reassure him, he could accept your feedback without feeling upset or deffensive about it.
Here is the web for a list of sex therapists.