Misdiagnosed blighted ovum?

My last period was 3/20 i have a 25-27 day cycle. I had cramping on 4/10 and spotting on 4/11-4/13 which i thought was implantation. i got positive hpt on 4/16. Postive test and dr and hcg looked good 272 4/19 and 676 on 4/21 I went to dr on 5/4 thought would have been 6 wks 3 days. They said they only saw empty sac told me looked like had a blighted ovum. The later called me and said there still could potentially be pregnancy but it was too early. Did hcg again 12128 and again on 5/6 14132. not sure what to get from hcg it nowhere near doubled but did go up. Is there still hope? I know i did ovulate late 3-5 days. I have read a lot of stories where it was too early and they were misdiagnosed and later test found fetal pole. I am not sure how to feel right now. I have no symptoms except for bloated, breast tenderness and very little nausea. I miscarried in august 2010 never got a positive with that one just a faint line. I have another ultra sounds appointment tomorrow a week since the last one. Any advice is appreciated.