I only just found this thread, and I'm wondering how the gym ball weaning is going? My baby is the same, he's almost 5 months old now and the best thing to get him to sleep since he was a newborn is bouncing on the fit ball. I still do it, but I recently got a bouncing hammock as a day sleeping bed for him. It has a similar bouncing motion to a fitball. It hangs in the lounge room just near the kitchen so I can be doing anything while he is asleep, as soon as I see it moving I just bounce it again and resettle him. I also wear him a lot and co-sleep too so I don't think he's going to have a problem adjusting to a bed later (apparently he can use the hammock until he's about 3 years old).