Lyme testing is very inaccurate. Even if he tests negative. He could still have it. The first screening test is the ELISA which is something like 40-60% accurate from what I've read. If that is negative, most dr's stop there and say no lyme. If you wish to learn more go to lymenet.org. There's lots of info there.
Patsy is correct. I recently saw an episode of "Mystery Diagnosis" and one of the top lyme disease specialists in the country spoke about how difficult it is to test for lyme disease. For one reason, there may not be antibodies present in that particular sample of blood and for another reason, a person with lyme disease has immune suppression and their immune system could be so suppressed, that they are making antibodies. In the case I saw, the specialist had him fill out a questionnaire and also tested him for encephalitis. Encephalitis can be present in some patients' who have lyme disease and the man on the show did have encephalitis.
I hope your husband's physicians' also checked him for autoimmune conditions. I would definitely find out as much as your can on lyme disease, through that link that patsy gave you, so that you can work with your husband's physician to get an accurate diagnosis.
"that they are making antibodies"
Change that to AREN'T making antibodies