Potty training all depends on whether your son is interested or not. You can try some different techniques and see if it will guide him into wanting to go on the potty. But he is the one that has to make it happen.
Bribes may be in order. Does he have a favorite activity? Or a favorite place to go? Maybe tell him if he can go for 3 days without a wet pair of underwear, you will take him.
No more pull ups. Only big boy underwear. Do not have them available for him to change them.. If you do continue with pullups, do not let him know where they are stored. He will have to ask you for a change of underwear. You may even tell him, "oops, we only had that pair for the day, I guess you will need to go the rest of the day wet or with your bottom naked."
Give him lots to drink and encourage a full bladder, when you see that potty dance or that expression, remind him not to get that one pair of underwear wet. Remind him to go quickly to the potty.
My aunt said she would have her boys watch cartoons while sitting on the potty chair at the time of day they usually went potty in their diapers. She said they would get excited when they went in the chair and started to understand "the feeling".
Have him watch your husband go potty, doing both pee and poo. Your son may want to try peeing while sitting facing the back of the toilet.
I know this is frustrating. He has to have a brain ready to process the whole potty thing, sometimes, it just takes a while to figure it out.