This may not involve a worker's comp claim unless your physician can indicate that the condition is being aggravated by your working conditions.
However, under the federal FMLA, employees who have worked at least one year for the employer and a minimum of 1,250 hours during that year are typically entitled to FMLA leave time for a serious health conditions, which can be taken in increments to permit you to go to PT. The employer cannot deny FMLA leave if requested and the statute prohibits employers from retaliating against employees for taking such leave.
In addition, if your condition substantially limits one or more major life activity, you would normally be protected under the ADA, another federal statute, which requires the employer provide the working stand you requested as a reasonable accommodation, unless it would be an undue hardship to do so.
Since the employer has already refused both of these, I would file a complaint with the HR department and at least consult further with a local employment law attorney to help protect your legal rights.
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