Sick days asking for proof?

Yesterday i was in drive-tru all day long, (it was windy) and i woked up feeling ill, i call the manager and told her i was feeling sick. Then she said many people call in sick because is holidays... i felt a guilt trip, coming on. She said I had to take a doctors note or else there would be consequences. Can employers do this when you work in food chains such as mcdonalds, wendy's , burger king ect? Is this also a form of harrasment?