Was the decision to begin the toilet teaching process started by signs of readiness in your son, such as him being uncomfortable in a wet or dirty diaper, or telling you when he had gone, or an interest in the toilet? If so, great! If not, he just may not be ready.
With most parents using disposable diapers and pullups, this doesn't give toddlers/preschoolers the incentive to use the toilet - even with those "feel wet" liners, when they pee, the moisture is mostly pulled away from their skin. A switch to cloth diapers or training pants can give them more incentive to not want to sit in a wet diaper, to know what happens when you pee (you get very wet!) and to know what it feels like just before that happens.
Telling you when he needs to use the toilet is often the last step in the process. With my daughter, she trained in 4 days at 3 years, 1 month. With my son, I started the month before he turned 3. I used thick cloth training pants with waterproof outside liner. I didn't wait for him to tell me or ask if he had to go. I just took him to the bathroom about every hour and a half during the day. The first couple of weeks, we went through every pair of training pants during the day, and after that, he figured out to wait to pee or poop til I took him to the toilet. It was about two months before he actually started telling us that he had to use the bathroom
Good luck.