Although you might be feeling a little frustrated, there's good news on the horizon: You are not alone! Plenty of parents struggle at this point - while some kids are ready and motivated to use the "big kids' potty," others are perfectly content remaining in the comfort of their diapers.
Could your son be afraid of the toilet? As silly as it sounds, some kids are scared of the loud noises! Or he may not be comfortable with the idea yet. Try starting out with a potty chair. You can buy a special potty chair that are lower (and often brighter and more fun looking) than toilets, and place it in the bathroom. This can begin to get him comfortable with the bathroom in general. Later on, you can move the seat part of it onto the toilet to help him transition to the big toilet.
If you think he needs some motivation, you might also consider a small reward system. The reward doesn't necessarily have to be something big like toys or candy - you'd be surprised how far a cool sticker can go! Try creating a chart for the wall, and letting him place a sticker on the chart for each time he successfully uses the potty. See how many he can collect in a week!
If you're still having trouble, I suggest you talk to your child's pediatrician.
Below, I'm including an article that you may find helpful.