It is possible that you might have narcolepsy, however, you also want to make sure that you are getting enough sleep during night as inadequate night-time sleep could lead to increased sleepiness during the day. In any case, you need to see a sleep physician as soon as possible as it is dangerous to drive if you are sleepy. In fact, driving while being sleepy is as dangerous as driving under the influence of alcohol. It is dangerous to not only you but also to others on the road. I strongly suggest that you see a physician specialising in sleep disorders as soon as possible so that you get proper assessment and treatment. Until you see a physician for treatment, you should avoid driving.