I go to confession often with different priests. Some priests seem to view certain sins as more serious than another priest would. If different priests tell you different things about your sins (whether they are mortal or not, etc.), how do you know which one is right?
Look up the issue in the Catechism of the Catholic Church. Whichever priest’s advice seems to adhere most closely to an official source like the Catechism is the priest to whom you should listen. I also recommend trying to find a regular confessor. Once you find a priest whose orthodoxy and spiritual maturity you trust, go to him for confession whenever possible.