I've been feeling like I'm in labor all day

But I'm a first time mom so I cannot tell, and only 29 weeks! I've been having random back pain and cramps/low pressure that comes and goes but that's just about it. I'm not sure if the back pain is due to sitting up at work all day but if anyone has any telltale signs of labor that will help me decide if I should I go the er, I'd appreciate it!