Confused!!! Thought Water Broke But Test Is Negative

Hey ladies,
i am 28 wks pregnant .Around 11:00 am on the 22nd I was standing and I felt something weird. You know when you have your period and you are wearing a pad and when you're standing you feel your self leaking and it feels warm and wet (unconfortable for me!)yuck!! Any ways I felt that exact same thing and I got worried. At first I thought it was just discharge but it was watery so I went to check and sure enough my liner was almost soaked. When I got home it was prety late. I went to bed at 1:30 am . I was laying flat on my back and I was trying to fall asleep when suddenly I had the same feeling except this time it was alot. My underwear was soaked and my mattress was like someone had spilled a full glass of water on it. I quickly got my husband up and showed him. He then decided to take me to the hospital. I was also experiencing about 9 contractions an hour but they were painless. As I was there they put me on the monitor and they tested me to see if infact my water had broken but the test came back negative. Acording to them my bag of water was fine but my contractions were constant so they gave me 2 shots to stop them. They checked my cervix and said that I was 1 cm dialated. After my contractions stoped they send me home and put me on bed rest and told me to monitor my contractions. My question is, if I didnt break my water, then what the heck was that... I am sure I did'nt pee cause I had just emptied my bladder. Is it possible for the test to fail? Please let me know if you have any thoughts. Thanks!