Breast examination is required to reveal the undelying cause of that pain .
Hi Haley, I am not a doc but wanted to suggest that the way u describe the pain it does sound like pulled muscles. Especially if u r doing heavy lifting. There are many muscles in the areas u have pain. I would probably see my gynecologist just to have a breast exam. I don't think u have anything to worry about.
Being under stress doesn't help for sure. Good luck.