Thank you for your query at DoctorSpring.com.
I understand your concern.
Miralax is acts by increasing the water content of stool, making it soft as well as increasing the stool volume. This way, bowel movements increase in frequency and constipation is relieved. So your soft and mushy stools are due to the Miralax.
This can continue as long as you are taking it. Once you are off Miralax, you can expect your stool to get back to normal. Meanwhile, make sure your fluid and electrolyte intake is adequate by taking good amounts of water, fruit juices etc.
Bloatedness is a side-effect of Miralax and it will go away once you stop taking it. Meanwhile, please avoid carbonated beverages and gas-forming foods. You can take an OTC Simethicone 80 mg, after every meal or as and when needed to relieve the bloating.
I hope this was helpful. Feel free to ask queries.