Ct scan of the brain found 7mm hypodensity on the pineal gland which may be a cyst. i have health anxiety and am stressing about this they want me to get an mri. is this serious?

Probably not but only the Drs who have gotten your history and done an exam can give a good answer. Why was scan done would be important to know. If not for pituitary issues then likely an incidental finding.

The MRI will help characterize the described lesion, and most likely this is a benign, lifelong pineal cyst of no clinical consequence. It is not feasible to accurately guess the severity of your lesion on this site.