I am having pain in my lower left side of my back.  It comes and goes over and over, kinda like contractions.  It will last a few hours to a day or so.  I can take pain meds and it helps.  It will go away for a few days then come back again. Can this be a kidney stone?
First get ultrasound to check if any stone is present. If report is not showing any stone than it can be muscle strain. I would suggest you to start Muscle relaxant like Moral or MySpace. Also, you should take warm water shower. You should also learn back muscle strengthening exercises from physiotherapist. It will give power to your muscles, so you would not have such pain in the future. Till than you avoid pizza delivery by bike.