Aww, hang in there, back molars are honestly the worst stage, a few of us went through this around the same age and it really does affect their appetite quite a bit! What helped our kids most was going cold and soft, chilled yogurt, mashed banana, soft steamed sweet potato, or even silken tofu all work well because there is minimal chewing needed and the cold texture soothes the gums at the same time. One of my mum friends also tried putting small pieces of chilled banana or cucumber into a mesh feeder, and she said her daughter was much happier gnawing on that than trying to eat proper meals. For the gum discomfort itself, a clean damp cloth chilled in the fridge for about ten minutes works wonders, just gently rub small circles on the gum area and lots of cuddles, it really does calm them down faster than you think!