Related to Pregnancy? UPDATE

I'm having this pain in my back, kind of beside my left breast, and it's super sharp every time I inhale.. Help?? ***UPDATE: I called my OB office this morning and they told me to go to the ER and be further evaluated and that I had to go there because my family doctor wouldn't see me since I was pregnant. So, I go to the ER and the doctor was VERY blunt and bland and just said he couldn't do anything but give me an XRAY to check for a mass or something, but he didn't think it was necessary, as it sounded like muscuoloskeletal pain, and told me to just take Tylenol.. but, he put on my discharge papers that I had an Upper Respiratory Infection. Anyway, I've been pretty much okay today, until I laid down tonight, and it got worse, and moved up to my actual shoulder blade. I'm really worried it's something more serious, but not sure what to do since I can't see my family doctor, and the ER says it's nothing. Can anyone help?