It sounds like you really are sick. I think that you should give your primary care physician
a call today and try to get seen right away. If this is not possible, then it is not unreasonable for you to go to the emergency room for further consultation.
Overall, it sounds like you have an infection (bacterial or viral). A sore throat
most often is due to a viral upper respiratory track infection but can also be do to the flu, strep throat, or mononucleosis. Back pains, chills, and nausea combined with a sore throat during this time of year sounds suspicious of influenza. For this reason you should avoid small children, elderly people, and pregnant women until you get checked out. Strep throat can produce these symptoms and can cause problems in the kidneys, though this doesn't usually result in back pain. Mononucleosis can cause a sore throat, chills, nausea, and an enlarged spleen. Again, back pain is not a common complaint. However, all of these conditions can result in muscle aches, which can manifest as back pain.
As you can see, the list of possibilities is long, and some of them require treatment. In addition, the list I just gave you is incomplete. Get to a doctor
as soon as you can.