What Causes Frequent Bladder Infections?

I have frequent bladder infections but now have pain (stabbing) in my mid/low right side of my back along with two days of constant watery diahreah and no appetite. I'm 52 pounds, very healthy and weigh 103 pounds. Could this be divirticulitis or kidney issues? I just started taking macrobid for the uti - should it help or do I need to go back to doc. Thanks, alicia