Man that doesn't sound like a good time at all! If you get stung by an insect, you can use household ammonia, and it will stop the sing immediately! Also plain OL meat tenderizer, with water, just make a paste out of it, and apply it to the sting site. Most insect venom is a Protein. I would definitely get a better doctor, than what you have, specifically one that deals with reactions like that. Maybe an allergist, or neurologist. At least any doctor who will take your symptoms seriously, enough, to at least refer you to someone that can help you. I don't think you will lose your leg, but you might get nerve damage, if you don't get to the bottom of this.
Wayne