Breaks at work.

I'm 24 weeks pregnant, I use to not take a break at work because I could handle it, now I can't, I get light headed, and it causes me leg pains & back pains if I don't have one. Well today, we were not busy AT ALL, we had like 2 customers within 20 minutes, and we had 5 people in the store ( the store is very very little, and small ), I asked my manger who is a man, if I could take a break, he said " well when did you get here " I told him 11 & it was 1:20 or so & we were very busy in the morning & I was running around, sweating a lot, hardly could get a drink of water because of how busy we were, but everything slowed down. ( he wasn't there it was a women that was there until 1 ). Well he said " you don't get a break " I told him " well I'm pregnant, I need to eat & sit down ", he said " I DONT CARE ". Yelled this to me. I bawled my eyes out on front line, no one knew, but I did. I than said, may I go home early, I am having bad leg pains, and back pains & I need to eat. And he told me to leave, so I did at 2. I than contacted my general manger, and told her what had happened & she said this " k " than " I'm on vacation " , I apologized and never got anything back. What should I do, I'm tired of getting treated like trash, but I need the money... I am required a break, I'm going to get a official letter from my OBGYN that says so, but it's a right for me. What do I do.