Mid Left Back Pain

42 yr old female, healthy, active, 140 lbs, 5 months ago had swine flu, coughed so much the muscles in between my ribs were spasming, took NSAIDS, got better, then was diagnosed with osteoporosis and received Reclast in March!  Since then, I've been experiencing mid left back pain, CONSTANT.  I've taken Mobic, Prevacid (just in case it was esophogitis) and had physical therapy, nothing helped at all!  The pain is a wavy type pain, it is only "better" when I lie down at night, but it never goes away.  It's especially noticeable when I'm driving or riding in the car, working at my desk, or just sitting watching tv.  It is not worse with movement or strenous activity!  I can work in the garden, bending over and pulling weeds, etc., it doesn't make it worse, it's just always there.  I'm not short of breath with exercise, so I don't think it's my heart, chest x-ray is normal!  I can't figure out if my coughing back in Feb did something or if I'm having side effects from the Reclast!  Help!