Soaking/bathing is a last resort only. The only time you should ever do it is AFTER your snake has a bad shed and has pieces stuck. Basically snakes create a natural lubricant between the layers of skin when they shed. If you bathe them while they are still in shed it can wash away this natural lube and cause a bad shed.
Now that the damage is done and your snake is having a bad shed, you need a solution. I recommend you take a pillow case and a small towel. Get them damp with warm water. Not soaking wet! Make sure you wring out the excess water. Put your snake and the towel in the pillow case and tie the end off and put them in your snake's cage. Leave your snake for a bit to crawl around in the sack. This usually helps get the majority of the bad shed off.
How big of meals are you feeding your snake? He should be getting 10-15% of his body weight ever 5-7 days. He is still young so he might not be getting enough food and uses up all the nutrients and has nothing left to poop out. Then again, some snakes simply don't poop often, but i doubt this is the case since you soaked him and 9/10 times when you soak your snake it will poop.
AKedit: Dang yall type fast!