Shoulder pain after sleep, please help? (giveing as much info to work with as i can) ?

I am a girl and 24years old. I have an athletic build making my shoulders a lil wider then most. Through out the day i do my best to keep my back straight and stand tall. I like to go for walks. Dont have as much time for as much exorcise as i like because of work (nurses aide, lifting never do alone with heavy lifts). I do dance a bit on that new kinetics game dance central. ~ I have a brand new plush top mattress that i have even went out and got a 4inch memory foam top to help with my hour glass like curve. I even use a pillow between my legs to try to even myself out. But i still wake up with this pain in the part of my shoulders about around and even into the lower part of the neck. I have tryed falling asleep laying in every other position i can but always wake in my natural one on my side. This is causeing me pain and seems sometimes headaches. Its also causeing me to wake up a few times at night and makeing the straps on a bra feel like i have more weight on my shoulders then my chest size (not for u perverts but if it helps its an annoyingly to heavy size of D36...so heavy :[...) ~ well i think i gave all i can for you all to work with. Can someone please help me find a solution or even something to help reduce this even a little? I would very much appreciate it. Please and thank you.