There is a lot of help available for this condition, which is actually very common. To feel some nervousness when you are driving is quite normal, and usually gets less as you acquire more experience. However, if you feel your fear is getting worse you may need to seek help.
You could start by exploring this website, where you can get help with identifying exactly what you are afraid of about driving and what steps you can take to overcome it. There are many treatments available, but you may find you can help yourself, so do try some simple steps first:
Just sitting in your car and practising using the controls, switching on the engine and getting ready to drive can be very calming. For your first drive, you could get a friend to come with you and just go a few hundred yards - or even get a friend to drive you to a very empty place like an industrial estate out of working hours, and have a little practice in very quiet conditions. You can build up from there, and it's also good to contact a driving school, explain your problem and get a specially trained instructor to give you a few lessons aimed at overcoming fear. If you still feel you need therapy, the driving school will be able to advise you. Good luck.