Phobia of highway driving

Dec 2020
Washington, DC
I have a major phobia of driving on highways, anything over 50mph. I also get very tensed when someone is following me and right up my ass pushing me to go faster. I almost go into panic mode if there are no shoulders when i'm going more than 45 miles per hour. My blood pressure is normal and I don't think it is high. It is definitely psychological. Any help and pointers on how to overcome this is greatly appreciated.