My DS will be 3 at the end of January. Last year when he turned 2 he was interested in potty training and actually used the potty a few times successfully. He then started getting really constipated to the point of needing meds to keep things flowing. While getting that all worked out the doctor advised not potty training so that he didn't associate the potty with these problems. So now that we have an all clear to train, he does not want to use the potty. We've tried potty charts with stickers. We've tried little prizes for using the potty. We've tried using a little kids potty and a potty seat on the big potty. Big sister is trying to get him to be a bid kid like her. He's really into pirates so we told him pirates don't use diapers and his response is that pirates throw the potty into the ocean. I have no idea where to go from here since DD trained herself at 19 months. Please help this potty training mom! 

My DS is 3 1/2 and still not potty trained
Did not happen. Was 3 1/2 before he was potty trained and he still needs pull-ups at night now(he is 5).
It can get frustrating but you just have to go with the flow.
As we neared her 3rd birthday, I started telling her that 3 year olds were too big for pull-ups. On the morning of her birthday, she put on a pull-up and smugly told me I was WRONG, they did still fit her when she was 3.
. They finally trained at about age 3.5. The one thing I learned is they will train when they want to train. I tried and tried but they were just too comfortable in their diapers. I would try enticing them to the potty, didn't work. They would run and hide when they had to go then tell me they needed a change