Potty training a dribbler

My son has been potty trained for 3 months (daytime only-he still wears a diaper for naps and night). He’s done really well and tells us when he has to go. But he’s been dribbling in his underwear almost every time he has to pee lately. He will dribble a little, tell me he has to pee, and then he’ll hold the rest until he gets to the potty. What can I do to stop him from doing this? He pees like 10 times a day and is going through so many underwear!