So I am 3 months late on my period I had two at home pregnancy test come back positive a blood test come back negative before one of the at home test i gained about  20 pounds over the 3 moths I went to the obgyn and they gave me a pee test and it came back negative he said I had a blighted ovum but I got a positive two weeks ago could they tell from just a pregnancy test no altrasound I never blead I never cramped?? Help?