A retroverted uterus is nothing to worry about. All it means is that yours tilts backwards in your pelvis instead of straight up. It is usually genetic so you may well have been born with it, usually there is no health problems associated with it and wouldnt affect conception.
If you are pregnant then usually by the end of the first trimester the uterus has straightened itself out.

Emma27 - if your contractions were mainly back pain then I would say this is most likely due to the position of your baby while you were in labour more than anything else. :-)