I use rice protein powder--I'm also on synthroid. No thyroid for me! It's yummy. Any HFS should have it. I also do Steiva b/c I don't tolerate sugar. It's not a direct one-to-one correspondance....IE: 1/4 cup sugar does NOT equal 1/4 cup steiva. I made bread the other day and couldn't tell the difference.
For IF, what about pureeing your veggies/fruit? I can tolerate much more that way...even refried beans are better than solids for me. I can tolerate V8 type drinks in small doses.
Let me know if I can help more. I am also a strict vegetarian who is dairy and mostly gluten free.
-------------------- IBS-C with major bloat!
Gluten Free Vegan