So is this teething?

Little man is almost 8 months and the past couple days he has been ANGRY. Usually he's cheerful, energetic, and laughs copious amounts, but since yesterday he's been scream-crying and clingy in a way I'm not used to. There'll be windows of time where he seems back to his normal self, but he'll only play if he's literally touching me, sitting between my legs or lying right next to me. When he cries he SCREAMS, screwing up his face and making the most rageful noises. He also puckers his mouth, which makes me think maybe it's the teething? Since month 4 he's been gnawing on everything and drooling a bunch, but still no teeth. Even now I don't feel anything under the gum or see any blisters.

Could this be teething or something else? How long until it passes? I just want to help my little man, he seems so sad!