Stress could be playing a major part in it hun, and if you can you need to be able to try and relax, for your health and bub's!

You need to do some gentle stretching exercises to try and relieve some of the tension in the muscles. Gently turning to one side, and holding for 10secs (go as far as you can without pain and support your position with your arms), do on other side and repeat 2 or 3 times. There are a few others but I'll have to try and remember them.