What are early signs of labor? very confused?

I am a little under a month away from my due date and at my checkup last week I asked what the signs of labor are and my doctor said the only sign ill see is my water breaking. He said that's the only way ill know but I thought there were other signs. The last 2 nights I've been waking up with menstrual type pains in my tummy, my back has been hurting and every now and then over the last 2 days I've been getting sharp twinges "down there" to the point where I have to adjust how I'm sitting. Are these signs of labor? This is my first pregnancy and I just want to make sure I don't overlook anything. Thanks!