Dear G., Hang in there! There are worse things than a 3 year old not being potty trained.
Start talking about big boy stuff!!!! Maybe one of the pull-ups have a character that he may like and want to wear.
I even went as far as to start looking at toys and showing him the age appropriate for. Separating baby from big boy. Big boys can go to Chuckie cheese.
I have six children- 3 girls and 3 boys. The earliest boy potty trained was 2 1/2 and the oldest was 4.
Now I do daycare in my home and I do potty train. Persistent, I ask every 15 minutes and I read books,(what does he like) sing songs. Washing hands became a bigger thing than peeing at our house. Special foam soap, a character bottle etc. Boys can stand up sometimes they think its more fun. They never learn to aim so, plan on cleaning the floor, walls, toilet everytime.
Stay calm, a child will feel and sense your frustration. This can cause problems.
I let a little boy pee out side one time and that did it. He never pee'd in his pants again. His mom was not pleased when they were at the college and he pulled his pants down in the court yard and pee'd. Don't give up. Some people say use a video, I guess I would try that. Letting your son pick out big boy underwear might help too. Good Luck B.