Opinions please.

This is my second baby & this pregnancy has been extremely different. I went into preterm labor at 34 weeks ( I'm 35 weeks today). All day yesterday I felt fine until the evening time, I started cramping horribly & had tons of pressure vaginally/rectally(plus sharp twinges down there), I even got super nauseous/dizzy headed . Today is no better I'm still cramping, the pressure is no better, the sharp pains are worse, & my nausea is awful! OH & not to mention I've had more bowel movements in the last two days then I have EVER had this whole entire pregnancy. What could this be?