Fix your posture (most likely bad), stretch your psoas and hamstrings, and go and have an ART or deep tissue massage done. You might also want to invest in a foam roller for self-myofascial release and then use a tennis / lacrosse ball once that's not enough.
I'd recommend buying this book: http://www.amazon.com/Trigger-Point-Therapy-Workbook-Self-Tr.... It shows you the trigger points which cause referred pain. I reference this book quite frequently and would also recommend (no joke) taking a woman's nylon and putting a tennis ball in it. You can then hold the open end of the nylon and hang the tennis ball over your shoulder with your back towards a wall. By applying pressure (by leaning) on the tennis ball for a few seconds, you can alleviate trigger points or sore muscles.
