Not potty trained yet

Vi

My son is over 2 and no where near potty trained. He is still comfortable in diapers and doesn’t tell when he peed in the diaper. We tried the training underwear and he peed in it and asked me to change it. I tried the reward method too. He tells me after he has pooped but not before. He knows how to sit on the potty and do his business. But he is just so comfortable with the diaper and doesn’t want to let go of it. Any advice?