Good points by the above. I would add that if your state is one of the many states that will be starting "Obama" care - you will be able to get insurance.
If you do have ADHD or ADD, one of the best ways to prevent it from interfering with your life is to learn all you can about it and then start dealing/coping with it.
This site should answer a lot of your questions - http://www.help4adhd.org/en/treatment/guides/WWK9
Also there is a great adult ADD site written by a person with ADD. They have lots of useful links and a lot of information. If nothing else its good reading to see how others are coping. The site is - http://jeffsaddmind.com/for-first-time-visitors
Hope this helps. Please post if you have any more questions or need more info. Best wishes!
If you are working there should be some type of health care plan that would provide appropriate coverage. If you are not working and/or depending on your income level you might quality for public health insurance. If there is no other way you can obtain coverage there are clinics with sliding scale fees.
Setting up an appointment after this is addressed would be the first step and then you could see what to do dependent on what they find. Keep track of and if possible write down any specific concerns you are having, how often they occur and if there is anything that can make them occur. This way they can know how to best help you.