Back Pain, Swelling, Took Medicines, No Relief. What Could Be The Cause?

Hi, On Friday my mid-back started to hurt on the right side of my spine . The length of the pain would be about 4 inches along my spine. Since Friday, it has gradually gotten worse to where it is swollen (to the right of my spine on the mid side) and hurts to move in any way. At first, I tried heating pads but they didn t seem to help. Ice seems to feel good on it when using it now. The only thing that takes the severe pain away is Tylenol but when it wears off the severe pain comes back. I m not aware of anything that would have caused this. I was doing physical activity on Wednesday and thought it could have been related, but I didn t feel any pain in my back until Friday and since it has gotten worse I m unsure it is just a muscle pull. Any thoughts to what I might have or what might help? Thanks