Could this be labor??

So around 1 am last night, I started getting really sharp pains in my lower left back side (felt like a pulled muscle) and eventually I got up to go to the bathroom(around3:30am) and that made it so much worse. It hurt so bad I would hold my breathe and it hurt when I walked also. 
Eventually it simmered down enough for me to fall asleep but than I woke up later (not sure when) to bad back pain and painful cramps. I fell back asleep . 
I woke up around 10 this morning and my back pain was on the other side now and it's constant and won't go away, it gets worse when I lay down. 
Is this just like back pain or is it labor...?