2 and half year old avoiding potty

We are on day 3 of potty training, it has all gone down hill. Day 1 we had 3 potty wees, day 2 we had one and then lots of crying when he knows he needs to go but doesn't want to, then a few accidents. Today is day 3 and we are tearing our hair out. He is happily avoiding the potty and just wetting himself now!! He is a smart boy and definitely understands, we are trying to be patient, use reward, encouragement and making it 'fun'. I'm just looking for some words of advice before we throw the towel in.

Has anyone had the same happen and what did you do to encourage use of the potty again?