You may want to consult in person with an employment attorney to get a careful evaluation of your situation. Your employer may not discriminate against you because of a protected characteristic (e.g., race, gender, etc.) or because you engaged in protected activity (e.g., filing a safety concern with OSHA). Otherwise, your employer has a great deal of discretion to manage its operation and work force as it sees fit.
My answers to questions posted on AVVO are intended to provide general information only, and are not intended to be legal advice. Employment law issues typically require a careful case-by-case analysis. Consequently, if you feel that you need legal advice, I would encourage you to consult in person with an employment attorney in your area.
I agree with my colleague here that management has broad discretion to schedule or discharge workers. From what you wrote, I did not hear any unlawfully discriminatory actions. With respect to your manager's comments, is there anything to it? Perhaps he was giving some constructive criticism and direction for you to improve. This may require a detailed conference with an employment law attorney in your area.
This information should not be considered legal advice or a legal opinion, and it does not create an attorney-client relationship. The information herein is general and for educational purposes only. A complete consultation, including review of facts and documents and research is required for specific legal advice or a legal opinion. You should consult an attorney for legal advice for your particular circumstances.