He might need to see a professional sex therapist - AASECT - Member Directory is the resource to locate one.

He also needs to have his GP know of the problem because there might be a physical issue - he reports feeling as if he were about to faint. It MIGHT be anxiety-related, but it also MIGHT have a physical cause, so the GP needs to be informed.

The most important thing for you is to make sure you do not feel responsible for his problem. Also, he should give you non-phallic sex. That seems obvious, but just mentioning just in case.

Good luck!