What Causes Lower Back And Hip Pain When On Medicine For Urinary Infection?

I am taking a new medicine for urinary infection, the name of the med is SMZ-TMP DS TAB I started yesterday evening and to day took two doses at the determined intervals... this afternoon I started to with bad pain on my bones in lower back and my hip and the bone on my left arm above the elbow, My blood pressure is 184 over 75 and heart beat 71 I am a female 63 year old and take several other meds. Wonder if this could be related to an interaction wit existing meds?