really confused any one had the same thing happen?

I have done 5 pregancy test and all positive 3 at home and 2 at the doctors a week apart he booked me in for a midwife appointment with the 2nd positive test, last 2 days had really light brown watery discharge so went epau hospital to have it checked out as I may have a infection. they did a scan and see nothing at all they then said they was doing bloods as it could be to early or eptopic or misscarage and that I would need to go back in 72hours to have bloods done again, but they called me now saying that bloods come back negative so I have had a misscarage and to do another test in a weeks time and it should be negative and that I should get AF in 4weeks.. what I don't understand is I have not had any bleeding or any cramps to show a misscarage... so I don't know what to think or what is going on.. how can I get 3 positive test and the doctor 2 and yet bloods are negitive... I am going to try see my doctor today to see what he advises but just wanted to see if anyone on here have had this happen and still been pregnant???