ADA reasonable accommodations do not include allowing you to miss work when you do not have PTO to cover the absence, unless you and your condition are eligible for, and your company covered by, the Family and Medical Leave Act and you could use "intermittent FMLA" for the medically related absence. You can find the FMLA rules on the U.S. Department of Labor website and should review them to see if they offer you any help. Otherwise, however, as stated, accommodations under the ADA do not include letting you miss work without using PTO (if you have any); you will have to schedule your appointments for sometime before or after work, or on whatever day(s) you do not work.