grrrrrrr.......

Ok I'm 36 20 weeks pregnant with my fourth and last child and had two back to back miscarriages last year... so my dr has told me that I have some further limitations then my previous pregnancies. I work at a preschool with 1,2, and 3 year olds all by myself I'm always getting hit or kicked by one of the kids when I ask for help no body comes and also I'm on my feet alllll day with no break. My job just says to me "well when they were pregnant they worked until the day they popped" with no restrictions so if they could do it so can I? I'm like wth all pregnancies are different and I'm older now and over weight so I have to be more careful then I used to and they still won't help me they just treat me as if I'm another regular employee.... I don't know what to do I got kicked in the stomach a few weeks ago and had to go see my dr cause it caused me to bleed.. and they STILL have done nothing what should I do?