6 days long fever with weird muscle pain

26M, it all started six days ago with loss of appetite & constipation, and also a high fever with the headache and dizziness that comes with it. Weird thing is, I don't have any problem with coughing or sneezing at all.

Day 4 I started defecating again and my appetite started getting better. I though the fever will be going away too, but it didnt happen. What did happen is that Im starting to get muscle pain whenever I do even the slightest stretch. It feels like a large amount of lactic acid had been built up in my muscle, exactly like the day after a hard workout, except I didn't workout and it is in my entire body.

What could it be? I have never had a fever lasting this long. I live in a very isolated location with no easy access to doctors.