Ash started dribbling at 3 months, so it's normal. Their teeth move around before they actually break through, sometimes for months! So it could be teething. I have found since Ash started dribbling at 3 months, he has also discovered a love to chew ANYTHING and everything, fingers and toys included, so I think he is teething.

Invest in some good bibs lol I have got a little system here, those smock bibs with a normal bib over the top, change the top one when it's soaked and still have dry clothes lol