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

Hi:
You should go back to your dentist to check the bite on the new crowns and adjust the contacts in between the corwns as well.  This could be an easy and quick adjustment that will provide relief.
Best,
Dr. Maddahi

If you do clench your teeth, you should make sure the bite is light against the lower teeth, and to get a mouthguard to help protect your new restorations as well as the teeth that rest opposing them. As for the tightness, that should go away, eventually, if you continue to floss daily to make sure the gums feel healthy and secure.