Potty Training Help

My son just turned 3 and we have tried potty training on and off for a little over a year now. We never really last more than a couple days before both parties want to call it quits. The problem we face is that at first he seems eager to use the potty, but after a day or two he just stops wanting to do it altogether. We’ve tried pull-ups and training underwear. Both ways he would either ask us to use the potty when he needed to or go when we would tell him we should take a trip to the bathroom. Then after a couple days he starts wetting himself frequently and resisting bathroom visits. He is pretty stubborn by nature so I feel like it makes this all more difficult. Has anyone successful potty trained a stubborn toddler? I need some advice! I have no clue what I’m doing..