If my lower back hurts when i run what am i doing wrong?

Shoes: It could be that your shoes are not providing enough padding and shock absorption. If your shoes are old, try replacing them with a newer pair of running shoes.Try running on a dirt path or in the grass instead of hard pavement if possible and see if this helps with your pain. Also, may be wise to do some stretches before running and see if this helps. Lastly, drink lots of water.