I've had all these symptoms for the past 3 months: nasal congestion, tired, achey body, headaches, dizzy, weak, sore throat, bad breath what could it be?

Chronic infection. You may well have chronic sinus infection, but this might not explain the weakness and muscle pains. You should be seen by a primary care physician and if necessary referred to an ENT doctor. Hope you are better soon. Why did you wait 3 months?
Sinus infection? CMD. All of the above are commonly seen with sinus infection, a common problem. Other causes as well. See a doc, get examined and treated.
Not sure. Could be flu what have you been doing for the past three months? You need to see a physician and get this taken care of.