You mentioned Miralax which is a warning bell to me. My grandchild was prescribed Miralax at a very young age, and developed horrid emotional reactioins. She had long-lasting unreasonable episodes of screaming and crying and was completely inconsolable to all efforts. She was taken off miralax, and after some time began to even out and become more able to interact. Research showed that Miralax could cause these situations and lead to possible permanent brain damage.
Surely, you have been advised to drink gallons of water and to try fiber such as Metamucil. Also, a vitamin, B1 or thiamin(e) could do a lot if you are deficient. I try to always use liquid or chewable supplements as tablets and capsules tend to pass
whole right thru my bowels with no benefit.