There are many things that can cause your colostomy bag to leak, like abruptly sitting up straight from a flat-on-your-back position can pop your pouch loose. So can bending over to clean out the bathtub, or picking up something off the floor, or stretching high to reach something. There are a lot of ostomy medical supplies that are specially made to help prevent leaks. Feel free to test out products and if your stomach isn't perfectly flat, try barrier rings and strips to help even out skin tucks and folds.
Learn to get in and out of bed on your side. Get in bed by sitting far onto the bed and going down on your elbow while holding the mattress with the other hand, and swing your legs up. To get up, roll over on your side and use your elbow to push up, while holding the mattress with the other hand and swing your legs sideways off the bed.
Get a clamp-type reacher for reaching down and use a stool for reaching high shelves. Learn to lift and carry on the side of your leg, carry things high, or drag it, or get someone to help.
Ostomates get hernias easier than anyone else.