Anyone know the law on restrom breaks in the work place?

I work in a prison. We have cluster dorms with 80 inmates in each dorm. There is no Officer bathroom in the dorms. I am a female at a male camp so there is no "using the inmate bathroom" for me as so many males do. I am also pregnant. Now I have asked for no special treatment since getting pregnant. We have 3 dorms that have restrooms but they put me on the ones without. Anyway, we have to cal for reliefs when we have to use the bathroom because we cannot leave the dorm unattended. I dont drink all nigth long and still get up every 2 hours to go to the bathroom so it's not like I am drinking a lot at work. I drink about 2 bottles of water in 8 hours just so I dont have to go as often. I still go just about every 1 1/2 hours. I talked to my boss about this today because I could tell it was getting on his nerves (not that he has to releive me). But he rudly told me that I need to limit my fluid intake and see a doctor because this was not normal for even pregnant women to urinate this much. And that I'm only 3 months and nothing is even putting pressure on my bladder yet. (my uterus is about the size of a large mellon right now so yes there is pressure and also pressure isnt the only thing that causes this. Anyway, don't want to get into the entire conversation because it really upset to be talked to like this infront of people and for people to see me crying. After asking him to speak in private. I was so upset I had to pull over on the way home from work and call my husband to pick me up because I could hardly breath. The cops stopped and wanted to call an ambulance but I didn't want them to. Anyway, does anyone know the rules for breaks? If there isn't a bathroom for you to use in the building you are in don't they have to let you go when you gotta go?