I'm sorry to read that your child has still difficulties with gaining weight. I'm almost sure that this was already tested, because it's pretty common, but just in case it wasn't: it might be "celiac disease". this disorder usually starts when you start changing your babies meal from milk to mash. It's sort of an allergy against a certain protein in cereal.
I hope that your baby will get better soon, my thoughts are with you, Carol.
