Root canal and crown still hurts after 2 years.

2 years ago, I had a root canal on a back molar plus a same-day porcelain crown; and an old gold crown on the adjoining tooth was replaced with a same-day porcelain crown. The back molar still hurts and is sensitive to pressure. I don't chew on that side. The dentist checked the bite, took new x-rays, re-filled an old cavity next to the formerly gold-crowned tooth. Each time, the crowned back molar felt a little better but it still hurts. Now the crowned back molar is also sensitive to cold.