So, what do you think it is?

Okay so I have been sick for three weeks now. I have had a cough that was really productive at first and now it is just dry and hacking sounding. Every time I take a deep breath it feels like my chest is tight, like there is a weight on my chest. I am really tired all the time and have back aches between my shoulder blades. What is wrong with me? I really don't want to go to the doctor if I don't have to...Oh and I have a runny nose, not necessarily congested (except for first thing in the morning), just constantly running.