How long do pre-labor simptoms last

How long do pre-labor simptoms last before you go into labor. I am 36 weeks and 4day's. I have loose stools, low appetite, and wake up in the night with strong contractions with baby pushing down so hard I want to cry it hurts so much. I have contractions everyday. But I'm not in true labor yet. How long does all this last before the real thing?