The employer has the right to require you to do your job--the one you had been doing. If you don't, even with a doctor's note, you can be terminated; the law does not require the employer to come up with a different job or different duties for you. If your employer is covered by FMLA (at least 50 employees within a 75-mile radius) and you are eligible for it (worked there at least a year; worked at least 1,250 hours in the last 12 months), then you should be able to take unpaid FMLA leave for up to 12 weeks. But if you can't use FMLA leave, then all you can do is use as much PTO as you have; once PTO is done (if you have any) you must do your job or be terminated.