My son is 4 years old now and just now is potty trained in the past month. At 18 months old, he was doing great and going every time I put him on the potty. Until his potty chair pinched him. It was one where the bowl lifts out of the top. He stood up, the bowl stuck to him, he sat back down really fast and ended up with a blood blister on his thigh. After that, he would not use the potty, even purchasing a new one/different style, he still wouldn't go.
I had talked with his doctor several times about him not using the potty. Her advice was...wait...when he is ready it will happen. All the punishment in the world won't make it happen until he is both physically and emotionally ready.
His occupational therapist agreed with this.
We would try every couple of months. Finally this last time, after the baby had been home a couple months, it worked. We had been talking to him about how he was big boy now and needed to wear big boy pants, that once the diapers were finished he would have to use the potty, etc. One night while he was asleep, all the diapers and pull-ups disappeared. In their place were 12 pair of underwear.
The next morning we let him wear his diaper until he peed. After that, we put on the underwear, brought the potty chair into the living room where he had easy access to it. The first couple times he peed in his underwear. He asked for a towel to clean the floor, went and set on the potty to finish. He went through about 4 pair of underwear in about 2-3 hours that morning. Then no more accidents that day. The next day only one accident. The next day only one accident. It has been just over three weeks now since the last day accident. He has only had one more accident and that was the other night while he was asleep.
We made a sticker chart. Each time he used the potty, he got a sticker to put on the chart and one to play with. We also did a happy dance for him and said good job, clapped, etc.
My advice is back off, give him a few weeks then try again. Getting upset isn't going to help and actually can make things worse for him becuase of the anxiety. If you are stressed over it, he will be stressed over it and will regress even more.
Boys tend to potty train later. Our pediatrician said that as long as they are 90% by 5 years old then there is nothing to worry about.
Relax and just let nature work on it! I promise he will potty train when he is ready and there will be NO stress if you let him lead the way.