wsu_beaver:If you were to fill your mask with water while being on the surface, put on the mask and tip your head back. Do you get water that runs into the back of your throat even when you put positive pressure into your nose?
I assume you mean water entering through your nose and down your throat?
As long as your head is upright, no water should enter your nose at all unless you breathe in. If you're exhaling through your nose, you definitely shouldn't have any water enter.
Are you able to swim or dive regularly (without scuba gear) with your head underwater? If so, it sounds like an issue of learning to independently control your breathing between your mouth and nose, because nothing should change just because you have a regulator in your mouth.