My diaphragm is killing me!!?

I'm 27 weeks pregnant and my diaphragm is absolutely killing me lately. Is it from the stretching or what could be causing this? I can hardly stand up straight anymore it hurts so bad. There's also been a couple of times when I get really sharp pains that make me immobile in this same spot. I've called my doctor about it and she wasn't worried at all. Has anyone else been through this? Anything I can do to ease the pain?