Your husband is way out of line. He doesn't need to go to a doctor -- he is not cleaning and wiping himself properly.
First of all, you need to tell him firmly and in no uncertain terms that you will not have sex with him until he takes care of this problem: tell him it is really rude of him to expect you to smell his poop and then be turned on by him.
I had a similar situation once, and I had to train my husband how to wash his rectum properly when he showered -- lots of soap and washing and rinsing. The other thing you can do in addition to training him to wash is buy baby wipes, and INSIST that he finish wiping himself by thoroughly cleaning with a baby wipe. Baby wipes are nice for all family members that way.
If he still really insists on being physically repulsive, you could try turning the tables on him, make him go down there, and see how he likes it.
It's possible he has encopresis, as stated below, but in my experience with men, it's probably just inattention to proper cleanliness.