Stress and mouth blisters?

it seems like whenever i am under high stress i get these tiny white blisters on my cheeks and gums, they are not thrush or cold sores but more like mini less painful canker sores. i think its correlated with stress because they show up during midterms and finals weeks. what can i do to stop it, its not really bad but i get paranoid that i have some other disease causing it which just adds to the stress