when your boss doesn't understand your situation...

So I'm almost 31 weeks pregnant. I was told my placenta was low which of course concerns me. I have been constantly told I need to rest as much as possible, so I try to. Its not to the point where I need to be on bed rest. I admit there are times I have to ask for assistance at work (lifting heavy items) and everyone's been pretty okay about it. The big boss sympathises with me since his wife had a baby about 5 months ago and she is expecting another. However he is barely around and I am stuck with my other manager. She helps me here and there, but yesterday she made me feel like me being pregnant was an issue.

We had a delivery and she listed all the big items, then said she was going to be nice and deal with it herself. I said okay (found it weird since she knows I wouldn't be able to carry them), then she went on to tell me about another woman that was lifting heavy items until she near enough gave birth. So I said everyone is different though. I already plan to talk to my midwife tomorrow to get some sort of note to show I'm not making it up. I have about 44 days left until I am off work then my maternity leave with start a couple weeks later. I just don't like being made to feel like I am a problem. Just wondering if anyone else has been through something similar?