How do I know I'm in Labor?

So this is probably kind of silly but with my first I never went into labor. I got induced in the hospital at 42 weeks. So now that I am almost 36 weeks and waiting for baby boy to arrive I have no idea what to expect. How do I know I'm in labor?! I'm having pains, Constants cramps not sure if these are what people call Braxton hicks or just pelvis tightening. So confused they hurt and are uncomfortable. Any one else have this problem?