I don't believe your fear of the dark is anything more than a phobia and it has nothing to do with OCD.
I wish I had some sort of magic solution for you, but I don't. Many phobias can be dealt with by simply avoiding what causes the fear, like if someone had a phobia about water, don't go to the beach, if you had a phobia about ferris wheels, don't get on one. But the dark? Pretty difficult to avoid. Dark happens. Every day.
Since your phobia causes you to have anxiety/panic attacks and could actually put your life, and the lives of others, at risk because of the way it affects your driving, I would suggest you look into some CBT. (Cognitive Behavioral Therapy) This type of therapy deals just with the problem at hand and will teach you how to face it, to cope with it, hopefully to rid you of it.
Some phobias may be irrational, but they are nothing to be ashamed of. I think being honest with your family and friends may be a good place to start. Trying to keep this hidden just creates more anxiety for you. I'm not saying this will be an easy thing to do. I would advise you to be prepared for some kidding and jokes at your expense, but I think when they realize that this is affecting your life in a very negative way, making you unhappy, unless they are very cold people, they will come around and try to help you. I have a feeling that if you open up about your phobia, others will eventually admit to a few of their own. That's what I would do, but it might not be the right thing for you to do right now. Perhaps your therapist would recommend holding off until you have a better understanding of it.
Perhaps others on here who deal with this same phobia will write and share their experiences and possibly what they did to overcome it.
Think about the therapy............you don't want to deal with this your entire life and it is "fixable."
Read some of the related discussions and you will at least realize you are not alone with this phobia.
I wish you the best.
Peace
Greenlydia