Throw the pull-ups away NOW if you really want him trained. They feel like a diaper, so he's doing exactly what he's always done in a diaper. I used to teach preschool, and they are the most awful product if potty training is really your goal.
All three of my boys were past three and responded to prizes. This may not work for you, but I had success with it three times. When I did this, we had had a potty in the bathroom for months and had also read Mr. Rogers' potty book many times. (One of my kids insisted that this book be read every time he went for a while -- a small price to pay.) I chose a week when I could devote my time to potty training. Then I took him to Toys R Us and told him that he was a big boy and that it was time for him to start going to the potty. I said that we were going to pick out some prizes and that every time he went, he got one of them. We got things like Hot Wheels cars, bubbles, balls, etc. -- about 20 things in all. It was a mix of tiny things and somewhat more impressive items. In addition, I bought a few things he didn't know about plus some suckers and other small candies. We also chose his underwear. We did NOT buy any toy or treat that he could have then -- there was only one way for him to get any of the things and that was going to the potty. By the time we got home, he couldn't wait to go to the potty. Of course, I gave him something he really wanted that first time and the next couple times. He was going constantly. I chose the prizes and mixed small things and bigger things, so that he continued to want to do it. After about three days, I ran out of prizes and announced that there were no more but that now he deserved something bigger any way. We put a sticker chart in the bathroom with a prize at the end. I don't remember exactly how many stickers, 25 or so. He got a sticker each time he went and the prize at the end. I think I did two sticker charts with one child and only one with the other two. By the time we were finished with that, they were trained.
We continued with diapers at night, but two of the three were dry at night within a couple weeks.
All three of my boys were past three and responded to prizes. This may not work for you, but I had success with it three times. When I did this, we had had a potty in the bathroom for months and had also read Mr. Rogers' potty book many times. (One of my kids insisted that this book be read every time he went for a while -- a small price to pay.) I chose a week when I could devote my time to potty training. Then I took him to Toys R Us and told him that he was a big boy and that it was time for him to start going to the potty. I said that we were going to pick out some prizes and that every time he went, he got one of them. We got things like Hot Wheels cars, bubbles, balls, etc. -- about 20 things in all. It was a mix of tiny things and somewhat more impressive items. In addition, I bought a few things he didn't know about plus some suckers and other small candies. We also chose his underwear. We did NOT buy any toy or treat that he could have then -- there was only one way for him to get any of the things and that was going to the potty. By the time we got home, he couldn't wait to go to the potty. Of course, I gave him something he really wanted that first time and the next couple times. He was going constantly. I chose the prizes and mixed small things and bigger things, so that he continued to want to do it. After about three days, I ran out of prizes and announced that there were no more but that now he deserved something bigger any way. We put a sticker chart in the bathroom with a prize at the end. I don't remember exactly how many stickers, 25 or so. He got a sticker each time he went and the prize at the end. I think I did two sticker charts with one child and only one with the other two. By the time we were finished with that, they were trained.
We continued with diapers at night, but two of the three were dry at night within a couple weeks.