i've had these blister like things on the inner side of my lips for two years..they never ooze, never hurt, never sting, never crust, never gone away since the i've noticed them.. i have no idea what it is..they seem to go away when i breath with my mouth for a long time..usually i do this before i sleep and the next day i see that it's almost gone..but they keep coming back ..these blister like things are on the inner top left and right side of my lips(when i yawn you can see it) what might these be???.. plzzzzzzzzzz help!!