Have you bitten your cheeks lately. Is this equally on both sides? Have your third molars or wisdom teeth erupted / come into the mouth? If the feeling is on one side it is most likely due to some trauma or infection. If it is on both sides reasons can be different,nit may also be that your mouth is more dry than usual and this makes your cheek stick to the teeth and you feel your cheeks are larger, Get your ears also checked, there maybe an infection.