Fussy baby! Help!

My baby is about 2 months a week away from being 3 months. He started having a lot of saliva when he turned two months, well now he’s been really fussy he will wake up eat just a little and not want to eat a lot he’d rather sleep. He usually eats all day but he hasn’t been lately. I think he might be teething but I’m not sure. Have any of you ladies been through this?