What would cause numbness in left hand and part of arm?

I have been experiencing numbness and weakness in my left hand and arm for the last 3wks or so. I am a 41 yr old woman and yes I do have hereditary heart disease. I have an apt. but cant get in for another 3wks. The numbness is mostly located in the pinkie and ring finger although the middle finger has a little numbness in it. The numbness goes through my hand up my wrist and the lower part of my arm. The weakness seems to get worse almost daily. I started off with little weakness and now have trouble lifting a plate. (feels like I could drop it at any time) I haven't told husband and kids because I don't want them to worry so if anyone has any ideas on what it might be please let me know. Like I said I do have a Dr. apt but not for 3wks. I don't want to go to ER because I don't know if it would be considered an emergency. Thanks for your help........