You're probably in hospital now, but the needing to pee thing would be because the pressure on your bladder suddenly changed, probably because a big fat head went clunk on top of it with the water gone.

My first waters broke with no warning on the couch - baby was high and there was so MUCH it was pretty obvious what happened. Bing 37 weeks I promptly freaked out, of course.
Second the midwives broke it because baby was sort of stuck coming out, they thought it might help, hoooboy it was the best thing they ever did, such relief!
Third they broke in the middle of a contraction and it was a very distinctive *pop*