Confused

So I was a week late for my period, I took four pregnancy tests and they all came back positive. I was so happy that I was finally having a baby. Well this past Sunday, I started bleedingand I got kind of worried. I went to the emergency room and they done bloodwork and said that I was not pregnant. The doctor couldn't really explain why so that next day, I went to My gynecologist and she done a urine test and said I wasn't pregnant as well. Neither dr. could explain why I passed four pregnancy test if I wasn't pregnant. If I was pregnant and I had a miscarriage, wouldn't that have shown up on the test? Or am I just the only girl they can pass four pregnancy tests and not be pregnant?