Sore back still

I didn't run yesterday or go to pump class because my back was a bit sore- I am sort of glad that I didn't go to pump because if I did then I would have thought that the back pain was from pump.
I did spend a lovely day at the Flemington Market and Chadstone- spending all the money that I saved from having an early night on Saturday. I also caught up with a friend for a coffee in the afternoon.
My upper back and shoulders were so sore by the time I went to bed and they are sore now so I have put off doing any exercise today as well. I might try to go to the gym in the morning and have a run on the dreadmill. I can't think of what else I am going to do. I can't not exercise but I am frightened of back pain and I don't want to make it worse.