Ok, I'm pretty new (6 rides on my bike and just under 60 miles) and I have no idea what proper bike posture is, I don't really know what I'm doing, I just get on and go, but I want to do it right. I am having a little muscle pain in my lower back, kinda where my kidneys are. It has been getting less and less the more I ride, but I would like to get it to stop completely. I'm probably doing it wrong. Any tips, or good sources to seek out?