I'm a 53 yo flatlander, running about as long as you but haven't experienced the symtoms you describe. Since this has been going on for 2 weeks now, it might be worth a quick visit to your primary care doctor. Maybe something is off in your bloodwork, maybe something else, or maybe just some over-training but getting a medical opinion would probably be the best place to start. Just my opinion, hope it resolves for you.
