Is my employment contract, namely non-competition clause, still valid?

I am a veterinarian in New York. I have worked for my current employer since February 2005. My employment contract specifies a non-competition clause for a 50 mile radius lasting 3 years from the end of the contract or last date of employment.

My contract was renewed in 2006, 2007 and 2008. The final contract was in effect until February 1, 2009. Since that time I have continued to be employed by this practice, but my employer chose not to provide a new contract. Instead, I am paid per day that I work, and my employer has also stopped providing the benefits that I had received under the employment contract (vacation and personal time, malpractice insurance, continuing education expenses, professional organization memberships, licensing fees).

I am planning to leave this position in 2012, and would like to know if my employer will be able to prevent me from practicing veterinary medicine. I have been willing to continue being under contract with this practice, but my employer declined.