My lower back hurts all the time what could it be?

Nerve or back muscle: It is common for a pinched nerve in the lower back to cause the symptoms you describe. Other causes are problems with your spine alignment, a disc between your vertebra which is bulging, or poor posture/muscle weakness. There are many other causes as well. If it persists, see your physician.

Lots of possibilitie: Most likely is low back strain caused by weak core muscles. Depending on the specific characteristics of the pain, there are other possibilities. If it keeps up please see your pcp to check it out further.