? About malpractice insurance

Hello I just had a couple questions about malpractice insurance. I know I need it and will be getting some soon. Is there insurance that I can buy that will extend backwards to cover me for what time I didn't have my own insurance? What's a good company to use?
No backwards insurance. Many people insure with NSO.

The other company, beside NSO, that gets mentioned most often that specializes in liability coverage for nurses is Marsh (www.proliability.com).