Cramping (contractions?), pressure, and nausea

37w5d. Dilated 2cm. Thinned out. Baby's low.
Since last night I've been cramping with a lot of pressure. The cramping feels like constant period cramps then on rare occasions will intensify but I'm really not able to time them.
Every couple hours the cramps (or contractions) will go away and then I'll feel extremely nauseous for a short time. Then the nausea goes away and the cramps come back.
Has anyone else experienced this? I've heard a lot of women say they had this just days before labor.