Thats a pretty open question you have here. Can you go into detail a bit more about what this pain feels like, is the weakness a tired feeling, or heavy, or you literally have less strength? Is the knee pain actually joint pain and do you have joint pain in other areas besides your knees, is the bowel issue cramping or regular but soft stool? when stretching or in general do your bones crack easy? Do you et headaches at all you would say stem from tension. And the fatigue, is it from the fact your body overall is not feeling well so you feel tired all the time? Sorry, who's asking who questions? Hahahaha!!! I look forward to hearing back from you.
Have you seen a doctor yet? This does sound flu-like and could be the flu or one of many other things, including Fiveomyalgia. Where are you located? If you are in a Lyme endemic area, this is also a common set of symptoms for acute Lyme Disease.
HI! How long have you been suffering with this. You could very easily have the flu, or some virus. If its been going on longer than 2 weeks, you should go to your doc. The symptoms you are describing could be several things, including fibro, or chronic fatigue syndrome. In the mean time, make sure you are drinking lots of water so you don't get dehydrated and my doc always tells me to drink Gatroade, mixed 50/50 with water. I do, but I prefer the taste of powerade instead. Good luck and hope you feel better.