I can't get used to my front crowns, they cause me discomfort.

My front crowns cause discomfort because they feel like glass against my bottom teeth. The crowns also feel very tight on my teeth to the point i feel like pulling them out. I also have sensitivity to hot and cold. What can the dentist do about the tight fit and the glassy feeling i feel. I'm scared to do anything strenuous because I may clench my teeth and scared they may break...