HI, I am a 15 year old female and two days ago I developed a fever of 101, but without a headache, sore throat, runny nose, etc. In fact I didn't know I had a fever until my friend made contact with my skin. The symptoms went away for a couple hours (I didn't take medication), but came back again. My lower back is sore and I'm feeling pretty tired. In fact I've felt out of breath and constantly tired for the past month now. What might this be?