What's wrong with me??

I don't want sex. Ever. I have an almost 6 month old baby and I breastfeed. My husband and I haven't had sex since before LO was born. Am I a bad wife? Should I just suck it up and give him what he wants? It's really starting to affect our relationship...and I do feel bad about it...but I seriously don't want to have sex. Should I go to the doctor? I really don't know what to do about this. Any help would be appreciated.