Doctors note for work.

Has anyone on here needed a doctors note for work? I work in retail and on my feet for 8 hours. I get light headed maybe once a week during the mornings so I'd usually grab a chair and keep doing my work. I either price clothing all day or tag clothing. I've sat down about 5 times so far during my pregnancy. Today it was brought to my attention in a mean way that I need a doctors note in order to sit down now. I kinda felt attacked. Got called into the office and then harassed a few minutes later. I'm going to get a note from my doctor but is there anything else I can do ?