EvilHorseOfDoom-Thanks, I'll look into that. It's strange, he's not like any of those other things you described your horse as. He is definitely not the lead horse in the herd and he is very dependent on our other gelding at home. He hates being away from him. We don't have any mares though, which is why we hadn't realized this sooner I'm sure.
AlexS-Sorry, I didn't explain that very well. He wants to try for another week and if he does not improve at all, then we will stop training and figure out what to do with him, but if he does improve (which our trainer believes there is a good chance he will), then we will keep going and probably keep him just to ride around our farm where there are no mares around.
Despite what it sounded like in my first post, he's really not a dangerous horse. He doesn't try to hurt anyone and has had kids climb all over him and he doesn't care. He stands still for the farrier, he climbs into a trailer with no problems, and he does great with groundwork. The only problems he has have to do with other horses.