I'm not sure what the back and leg pain is. I wish I could help you more but I'm not a dr.
it also just could have been the length of your cycle. but I would suggest you take a pregnancy test just to make sure. I hope this helps you and good luck
if you only bled for one day, there is a chance of pregnancy. anytime you don't have your regular cycle there is always a chance of pregnancy. have you taken a pregnancy test?