T.S.
I am an Exercise Physiologist specializing in prenatal / postpartum fitness. The symptom you are describing is very common. As the pregnancy puts strain on different parts of the body, postural changes develop. The muscles of the chest tighten and the muscles of the upper back and neck become overstretched, causing the pain you are describing. To alleviate the issue, rry to sit and stand up straight as much as possible, pulling the belly-button in and keeping the chin up. Do strengthening exercises for the upper back (rear delts and lats) and stretch the chest and anterior delts. The best stretch for this is to stand in a small doorway with arms in the door jam, 90 degrees from shoulder so the forearms are pushing on the doorjam. Push gently into the stretch, keeping knees bent, chin up, and shoulders down. You should feel the stretch near the shouler joint.
We offer a class that teaches how to prevent and fix the postural and abdominal damage that pregnancy causes, called Tummy-Time for Mommy. Check us out at www.bigbellyfitness.com. Let me know if you have any questions.