With how far a long you are I wouldn't be too worried unless you are having contractions, I think you should be okay. But if you are worried, you can call your OB in the morning and see what they tell you.
ETA: You are due in like 2-3 weeks, if you do get contractions is really nothing to worry about either.
as far as I know its only suppose to be a day or so. Is it a lot of spotting or just a little bit here and there. Sometimes I have a little spotting here and there and the doc said that it was okay. If its a lot of spotting, I would call ob tomorrow, just to check and make sure.