So, based on the additional information you have provided, it looks like Walmart did not violate their own policies when they terminated you since you were terminated for serious misconduct. Even if you were not guilty of theft because you had already paid for the product, then if they have a policy about filling your own prescriptions you may have violated that. I don't know, but based on my very limited information about your case, they may have terminated you lawfully. If you believe that they did not, then if I were you, I would consult with a local employment law attorney and see what they think your options are after you give them all the specifics of your employment history, etc.
As for your pay, you may have a better chance in getting back pay based on the fact that some pharmacists are categorized as hourly, and therefore covered by the overtime
provisions of the Fair Labor Standards Act, and some are considered exempt and not covered by the Act. In your case, Walmart has categorized you as exempt, because of that you were not entitled to overtime. The problem with that action by Walmart, is that if you have essentially the same duties and responsibilities as the hourly pharmacists, then you may under the eyes of the law, really be a nonexempt employee and entitled to overtime. Walmart is notorious for their problematic employment practices, and this is one area where they have made some errors in the past. If I were you, I would consider filing a complaint with the Wage and Hour Division of the Department of Labor
for violation of the FLSA based on misclassification as exempt. You might also want to speak to a local employment law attorney about this issue too, so that they can compare your job description/duties with that of hourly pharmacists to see if they are similar enough to be considered the same under FLSA.