Honestly, there is no way to know. You probably will have the baby soon is you're already 3 cm and having contractions, but it depends on a lot of factors (and "soon" is a relative term.) I started having regular (but weak) contractions on a Friday morning, but they never got much stronger and over the next couple days, got a bit further apart, even though they were painful. My water finally broke on Monday night,, and then I finally got to the hospital (at 4 cm). I had my son Tuesday afternoon. So basically, I felt as though I was in labor for a REALLY long time because it just wouldn't get going.
It's impossible to be patient , but just get as much rest as humanly possible right now. Good luck to you. :)