Well im guessing he probably drinks more in the daytime than he does at night time?...Which will obviously lead to him needed to pee more in the daytime, all i can suggest is that you every now and then ask him if he needs to use the potty and if he says no then just remind him that he doesnt have a nappy on and that he needs to use the potty when he needs to go!!... My son is 3 next month and find he's totaly dry in the at the moment, he seems to enjoy using his potty now!..i encouraged him with a potty chart and stickers so that he may want to go more to earn a sticker and after the charts full reward him with a toy or something!!..... also let him decorate his own potty with stickers ect....good luck with this =]
My son went through this for quite a while. I found that letting him be in diapers or training pants made the situation worse (not that I am disputing the previous advice - it just did not work for my son.) Is he having accidents while he's busy with something else? I ask because my son would be playing with toys or watching his favorite TV show and choose not to go to the bathroom because he didn't want to "miss anything." He found going potty to be a chore and a waste of time. It may be helpful to notice his "potty dance" or when he normally has to go - you can remind him or ask him if he wants/needs to go potty. I still have to stop my son and ask him, once in a while, because he thinks he can wait or just doesn't want to stop what he's doing - but no accidents for 2 years now. Good luck!
Keep him in diapers or pullups for a while and let the pressure ease on the potty training issue. 3 is a little young for a boy.