Employment Law Questions? Ask an Employment Lawyer.
Dear Grand Rivers, Kentucky:
If you were terminated, you might have some ability to sue for failure to accommodate a disability under the Americans with Disabilities Act (ADA). Here's a link to their website: http://www.ada.gov/. However, it might be difficult to prove violation of the ADA because it sounds like you are not quite disabled -- although you may end up that way.
HOWEVER, from what you are describing, it does sound like your employer should be advising you about the Family Medical Leave Act (FMLA) so that you can take leave to get better. Here is a link to FMLA regulations: http://www.dol.gov/esa/regs/statutes/whd/fmla.htm.
Under FMLA, your employer needs to give you up to four months off, although the time off does not have to be paid. The employer needs to hold your position open, and keep you on its medical insurance plan (although you may need to pay premiums).
If your employer will not accommodate FMLA leave and terminates you, you will have a cause of action.
Your doctor probably will need to certify your leave, so contact him or her for that.