My right shoulder is lower than the left one and theres a cracking sound!

I don't know how it happened but about 2 years ago my shoulder seemed lowered than the left one. At first there was no pain but about a year ago I started hearing cracking sounds. Whenever I move my shoulder in circular motions or up and down (since it's lower) it sends shocks and pain all down to my thumb. My arm gets so tense and stiff that my veins pop out! I use Aspercreme to stop the pain but it still hurts and my shoulder area to my neck is stiff and painful. Whenever I pass my hand through my right shoulder I can feel a knot and it feels inflamed.