Back muscle strain?

Hey guys!

Just need some advice. A little over a week ago my back started to bother me. At first it was just an itchiness right under my left shoulder blade and after a few days it turned into a sharp pain that faded in and out. It was bad Thursday into Friday so I just did a 2plus mile run on Friday and did a VERY light leg day. Friday was an ok day until later. Then it got pretty bad. I applied heat to it. Saturday it was lets say an 8 out 10 (10 being very painful). Sunday I felt pretty good. Not much pain. Here an there I felt it. I did take off Sat, Sun & Mon from the gym. The whole time I have been applying heat/ice. More heat though. My fiance gave me two muscle relaxers which helped the two nights I took them. Anything else I should be doing? Stretching? I would like to get back to lifting since its been a while but I know I need to rest my back up? Any advice on what I should do to prevent this from happening again?

Thanks! :)