Hi tylann mummy,
How old is your baby now? And how long has he been rejecting FM?
Yes usually teething will affect baby's appetite. It affects my baby. Solids will also affect. Usually my baby will only take 60-100ml of FM after his afternoon porridge. Usually he will take 150ml-180ml when no solids like his night feed.
It could also be that your son prefers solids to milk. My friend's baby prefers porridge and eats one big bowl of porridge for lunch. He only drinks about 400ml of milk a day. But because of that her son is very skinny. At 1 yo, he weighs only 9kg.
But even if your baby is rejecting FM for now, try to ensure that he still has enough fluids throughout the day to prevent dehydration. Try to make sure that he has about 6 wet nappies/diapers in a day.
Give your baby some time if he has only just started on full FM to get him accustomed to the new taste. It could also be the taste of the FM that he doesn't like.