Medical info revealed and rumor spread about me

Hello all.

I'm sort of looking to gage how angry I should be about this. I (30 F) have been teaching at my current school for a year. I'm on a probationary contract. This year has been bumpy, to say the least. Crazy parents and unruly kids, but I have been doing my best and keeping up fine. Anyway, I took a medical leave for a day last week because I needed to go to a lab to get an ultrasound. The ultrasound is due to recurrent bladder infections that are not coming up in the tests doctors' have been doing on me. To confirm they are bladder infections and nothing else, I went to get this ultrasound. In my medical leave submission, I just wrote "ultrasound" under the reason section (I was told we must add a reason for appointments).

A few days later after at school, a friend pulled me aside to ask how I was feeling. I didn't understand the question and thought our shared class of students had said I was acting strange or something. When I said fine, she said a rumor had been going around the staff that I'm pregnant. I was caught off guard, but immediately realized the source of this misconception had come from my confidential medical info someone from admin must have shared with our colleagues. My friend did not disclose to me who the person was who approached her with this gossip, and I didn't press. I was just happy she told me. Apparently people said I have been "looking" pregnant too, which hurt my feelings. I'm not a skinny person, but my BMI is fine for my height and I workout 3 times a week. I do my best to eat healthy. This year has really challenged me, so maybe I have gained weight, I don't know.

I went to my admin about it and said I didn't want to make a huge deal about it (I'm only probationary), but the more I think about it, the angrier I become. How would you folks handle this and has anything similar happened to you?