Sudden shoulder-bicep weakness – what is it?

i sure hope someone can help me!!! about a month ago, and out of completely nowhere, the right side of my upper arm got weak. i am a weightlifter so it is noticeable. i would say that, generally speaking, there is about a 10-15 lb. loss of strength in my right arm now. this is frustrating. i’ve been trying to work thru the weakness but it’s not going away nor is my strength improving. there is no pain, but i’m now noticing a tingling sensation in the crook of my elbow. the weakness doesn’t seem to affect (much) my triceps and back work – only shoulders and biceps work. what do i do – take time off (which goes against every fibre of my being) and rest it til it gets better or work thru it? what can i do to ensure it heals? and why the heck doesn’t it hurt?

thanks in advance for your insights…