My husband has had sever diarrhea, stomach cramping, back pain, and anal fissures for years, told it's not crohn's, what is it?

Can be several thing. Has he consulted with a gastroenterologist? If you are considering somebody in the area, i'm happy to give you some recommendations. Everything you are describing can be secondary to the severe diarrhea. There are several things that can lead to this. He should be seen by a good GI doc for full eval and treatment.