Could baby be teething?

My baby is 12 weeks. He will be 3 months this week. But for the past two days, he nyams at his mouth like he is chewing or making lip rub on gum. He also eats at his hand differently from the suckling of fingers he had learnt a few weeks ago. Before that, I noticed his stool was runny but I thought, probably he ate on STH dirty or STH. Ftm here. And yes he started drooling like more than a week ago if not two, and I thought it is a growth thing.

But I was at a family birthday party and two people told me he could be teething. Then mom mentioned that grand ma told her she got her teeth at 3 months. Now I can't get it all out of my head. My baby can't even hold stuff and is just beginning to tap them as he disco his hands last week. So I can't give teethers. Am a FTM and I don't really know if he is teething or not and what to do in case he is and can't hold teethers.