How can I get over my fear of highway driving?

God.. it's such a scary experience. I know its all in my head, but just the thought of getting lost on the highway is unbearable. I also feel like i'm trapped and that I might hit another car. I'm afraid that I might not be able to switch into the right lane and miss my exit and get myself lost. I know its crazy. but I cant seem to get rid of this paranoia. Help?