Oh yeah teething never helps, he was always fussier, didn't eat as much when he teethed (and who can blame them when it must hurt to eat)

Maybe a chat with a GP about food/sensory issues is a good step as well (I know that's where my friend picked it up - she had soo much going on that it took until her 2nd child to realise his eating habits weren't normal)

Goodluck