Family Dollar complaint: Mask medical condition

I walked in family dollar and the clerk stated I needed face mask to be in the store and I told her that I had a medical condition.She then stated I still needed a mask that I had to purchase and proceeded to hand it to me,I then got my items and went to the register and when I got there the clerk was telling another clerk about the encounter with me and the mask and my medical condition.I then told her I had a medical condition and she stated I wouldn’t be allowed back in the store without one.When did dollar store employees become medical professionals? If I have to sigh a waiver for my doctor to discuss my medical information with other doctors when is it ok to discuss it with an employee at a store!Since when is it ok to impede on someone’s CONSTITUTIONAL AND CIVIL RIGHTS! If I am denied entry in this public place then I will be filing a lawsuit!