Arms feel like rubber?

I play golf and recently my arms have been feeling like jelly. I can only chip and putt because when I try to take the club back for a full swing, I can feel how weak it is and have to stop myself from making the swing. I don't know what is wrong with me or how to fix it. I can't tell if the swing feels as though it is weightless or if it is 100 pounds but it feels wrong and weak. If anybody with a medical opinion knows about golf, I could really use the help on how to fix this problem as I have a tournament in a few days