My 20 week old had to have an Colostomy when he was two weeks old. The doctors told us that it wouldn't interfere with doing 'tummy time', however, the way I have to have his bag on him is across his stomach (otherwise I have leaks and 53268911 loads of laundry a day) and this does seem to bother him when he's doing tummy time. He's a very strong boy and can sit and stand and hold his head out very well, but I'm concerned that his 'core' muscles are not being strengthened. Any ideas on alternative 'exercises' we could do to strengthen his back?