How do I know for sure?

I'm sitting here at 5:12 in the morning. A contraction just ended and I'm wondering, yet again if this is it. I've had a rough few days of all signs pointing to labor and then after about an hour at the hospital, everything stops. I've been sent home twice and have been pretty disappointed about it. My mood is melancholy and my hopes are low. But I do know that the baby is healthy and I'm healthy, so we're good there. It really isn't a matter of impatience. Of course I'd like to be done being pregnant and be holding my baby, but I can be patient with that. It's the build up and the huge let down that is wearing on me. 5:19 another contraction. They've gone from 12 to 8 to 7 min. apart. I think I'll go take a hot shower now. Will post more later.