Labor???

I've been having contractions all day and really bad back pain. The contractions vary - they can be 2-5 minutes apart and then not be for another 10-20 minutes and they all hurt the same. I'm pretty sure I lost my mucus plug today as well. I was in the hospital for 3 days and they told me I was 2 1/2 cm dilated already and I'm not due until 12/21. I am extremely shakey and nauseous and have had diarrhea for like a week and have the worst pains. Could I be going into labor now or any time soon?