Early maternity leave

Is anyone on early maternity leave? If so how many weeks were you when you took leave?   I have been having really bad pressure pains at work because I'm constantly on my feet and sometimes I am unable to stand for more than 20 minutes at a time or I just go home due to the pain. I recently had to leave work to go to the ER because the bad pressure pains. The doctor told me the pressure pains are normal but they are starting to effect my work performance and I'll only be 5 month in a few day. Has any else had the same experience? I have doctor's appointment on July 5th, I was wondering if my pressure pains could also be because due to me having a low lying placenta.