What do I do? Why is this happening

My baby is 4 months and 2 weeks he was normally only breastfed for the first 2 months and after that broth formula and breastfed.. Today I tried giving him a bottle and didn’t want to eat and he was very fussy. So I tried breastfeeding, he would attach to it but then pull out and cry and ended up falling asleep. He woke up and he seemed fine for a while then started crying till I attached him to my boob again and fell asleep.. he sucks on his hands a lot and grabs my hands and my husbands hands and nibbles on out fingers... trying to bite.. it was around the time when I would normally have to feed him again but didn’t want to eat but was awake and then began to be really really fussy again... and went to sleep again... I don’t know what to do to help him... I don’t m ow if he’s teething or possibly getting sick. I’m not sure.

If you guys have any advice please share them with me.. thank you!