I agree with Duckie afterall she is a nurse. I thought that I had a UTI, and got the meds etc two days later I ended up in the ER in the worst pain I've ever had. It was kidney stones. I had a ton of little ones in me, and man did those little bastards hurt!
You should to see you doc, and make sure it's not your kidneys. Good luck I hope you are feeling better soon. Oh yeah you are doing just fine on your weight loss.