Can the doctor give wrong positive test?

just 2 weeks ago i took 4 pregnancy test and they all came back positive. so i went to the health dep. in my town and they told me the same thing i was preg! i was so excited. they got me started on everything a pregnant woman needs. i jus had an appointment with my OBG doctor and everything. but just yesterday i started spotting then started bleeding kinda heavy but i questioned how am i preg. if my pd. is on. ive heard that can happen sometimes but i went to the emergency to be for sure and all they did was a urine preg. test and told me i wasnt preg! i couldnt believe it. i jus felt so confused and sad about the situation i jus dnt understand how 2 doctors got 2 different results on the test? could i have suffered a miscarriage or possibly never preg?