I've had a similar problem and it was associated with disc compression in my neck. No symptoms in my neck itself, but nerves were compressed between the discs which caused pain, tingling, and numbness down the inside of the left arm, under the armpit, and even into my fingers (mainly thumb and pointer). I can definitely relate to the "asleep" feeling! I'm just completing about 3 months of physical therapy and am almost back to "normal." I've had to modify my workstation at work and keep up with home exercises and really be careful not to crane my neck on the bike. Had I not gone to the p/t I never would have guessed that this was related to nerves in my neck (cervical spine). I thought I had pulled something in my shoulder when lifting my bike overhead. Anyway, I'm not saying this is what is going on with you, but I am saying that it's best not to guess at what it is and get in to see a specialist who can diagnose you correctly. The sooner you get a correct diagnosis, the sooner you can start taking steps to remedy the situation. I doubt you want it to get worse than it is!