My body aches and I'm fatigued is it a virus?

I was sick about 4 months ago I had bronchitis and a sinus infection. I didn't go to the doctor and it took about 3 weeks to get rid of it. Well 4 months later my body aches like my muscles and joints sometimes and I'm fatigued. I don't have any fevers or chest and sinus congestion. I went to the doctor and they did a blood test and it said my white blood cells were low but nothing they would be concerned about. I also tested negative for epsteim bar and mono. The doctor thought I might still have a sinus infection so they gave me a steroid shot and it didn't make me feel any better, this was a month ago. I'm not sure what it is or why I feel like this any ideas? I'm starting to get worried ><