signs of labor?39 weeks pregnant

I am a first time mom and do not really know what to look for other than what my doctor says about contracts and how far apart before I go in. All last night my stomach was hurting so I decided to get up and walk . Moments later I didn't even make it to the bathroom I vomited outside. It was like a waterfall! I couldn't sleep I had to try to sleep sitting straight up and this morning my stomach is hurting the same. It feels like I have to go to the restroom but when I go nothing comes out. Mild stomach ache that doesn't go away. I feel baby move every so often so that is good I believe. Is this normal? And has anyone experienced this. I am 39 weeks pregnant.