I need advice...

Hi everyone, I am in need some advice. In all honesty I have an idea of what I need to do, but I don't know how to go about it in my situation. I'm 17 weeks and 5 days today and I am a shift supervisor for Starbucks Coffee company in washington, DC. Recently (give or take a month ago) I was moved from my last Store in the Georgetown area because I was being bitten by rat mites and the rats were in the cieling and the smell of the deceased ones always made me sick. The new store I am at currently the manager treats me horribly and it's gotten to the point where I have had a nervous break down. There is a whole bunch of drama I side the store and this manager feeds into it. The manager yells at me all the time, in front of the baristas and in front of customers and I have approaches him about this. He also makes it seem like a problem if I have to use the bathroom, get a drink of watee, or trying to snack because I am always hungry. This manager does know I am pregnant and the way he treats me is getting worse. I know I need to transfer out because I know I won't be able to handle this kind of treatment until September. My question is how can I tell this manager that I want to transfer because this whole environment is putting me under a lot of stress and dread going into work now and my anxiety is getting worse. Anything helps.... thanks...