I have extremely bad back spasms at night only that stop me from sleeping and then ache all day. What could this be?

Many things. Back spasms may be the result of degeneration of the spine, tumors, infection, herniated discs, or other non-spinal problems (such as issues with the kidney, stomach, etc.). If the symptoms continue, seek medical care. Pain at night that wakes you up is concerning and should be evaluated by a physician.