Ditto for my school.
It was tough when I was expecting, especially with my second when I had morning sickness. I was lucky though: I had a small class of good seniors. I kept a special trash can by the door. I'd step just outside the door -- the way people do when they're blowing their nose -- I'd throw up, then tie the bag in a knot. If you've had morning sickness, you know that it isn't like sickness-vomiting; it's less violent, and it's over quickly. I kept it lined with several bags so there was always another one there, but I rarely did it more than once a morning -- and usually once I'd thrown up once, I was done for the day. I think my students knew what was up, but they were a good bunch and didn't say anything.