Is your stomach getting hard with the cramps? If you are having contractions, your stomach will get hard. Some women vomit when their contractions get bad, but I don't think it's super common. The running stomach is more common for labor. Do you have a fever?
Call your doc first and see what she or he think you should do. I'm 34+5 and my tummy been messed up to but no vomit and I've had slight back pain but not unbareable call your doc honey better safe than sorry