I am so glad to hear she is doing better. I had a 'similar' case with Maddie last summer, I think.
( I forget when what happends these days) She wasn't pooping, vomitted when she ate and then quit eating. She too is a bigger girl and and lost a few lbs in no time. After a day or so, we saw the vet.
They did an exray and immediatly saw a blockage in her GI. Next step was a fecal exam, I guess is whay you'd call it.
What they pulled outta her bum was wood!
She had found some mulch to chew on while in the yard and it became lodged.
I woud've driven myself crazy had I not know. I hope get an answer to what it was causing the problem, but I again, happy she appears to be recovering.