I too had the same problem and I also use a 6-pak of boost daily. Who would think being constipated would be a problem on a liquid diet? But i too take pain pills for my throat which causes this. What i do is through my peg tube is do 1/2 dose of MOM daily, start off with full doses every eight hours till results then back off to 1/2 dose. This has worked wonders for me as seena s and metamusil gets laughed at in my system and doesnt touch a thing.
As far as your mouth pain my prayers are with you and im so sorry about what your going through. Not sure if you tried the triple mix for right before meals or not but might be worth a shot.
I sure hope these things help you be more comfortable and will check back for your response.
BLESS YOU
Bob Grey