Minni2906-
Hang in there since that hb is okay. It's the COMBINATION of measuring behind, spotting, and cramps that's a big red flag. I bet you catch back up next appt. If she used a very basic machine and this appt. wasn't at your sonographer or the ER where they have high tech ones, that could be it. For peace of mind, you could also go to the ER for a second opinion.
How sure are you about your dates? I charted so I was 100%...is it possible you got some early evap lines?
I'm not 100% but I'm fairly certain. I mean, before bcp I ALWAYS had a 32 day cycle. Like clockwork. Going by that, conception would've been June 29 which makes me 8 weeks tomorrow. (Still a ways off from what the scan said.) My scan was done at Advanced Radiology by a sonographer so I think it ought to be accurate.
Minni, your conception date could have been earlier than the the 8th (it most likely was if you got your BFP on the 12th). The zygote could have taken a while to implant and the baby can't start growing until it implants. That's why it's hard to know date of conception even with the baby's measurements. Two babies in two different women could be conceived on the same day but one zygote implants faster, so the due dates (and measurements) could be different even though they were conceived on the same day. Were you charting? Did you have an estimated day of when you thought you conceived?
If that's the case, would I still have gotten a positive even if the baby wasn't growing yet? I wasn't charting but I'm fairly certain I conceived June 29th as my cycles were like clockwork.
I temped, charted, and did OPK's because I know I would have gone crazy if this happened to me....because with my MC I measured a week behind and had not charted. But, I also bled and cramped
So you're guessing that conception happened on June 29, but here's the thing:
My charts:
TTC Cycle 1: 28 day cycle with bfn. Ovulated Day 15
TTC Cycle 2: 28 day cycle with bfn. Ovulated Day 16.
TTC Cycle 3:

July 12. Ovulated June 28 on Day 13. Last period: June 16
See the wide range DESPITE me having a bang on 28 day cycle?
Periods are also different after BCP.
In other words, I mean to me you could ovulate late...
With a 32 day cycle-----you can o as late as say day 20 and still have a 12 day luteal phase. So your conception date changes from where you think it was at what like day 16/June 29 or whatever, to 4 days later on day 20. And then how long does it take to implant--it can be 6-12 days beyond that. Hope that comforts you

I think it's good that you can't really be sure...I charted so I would have lost my mind if they didn't measure bang on. But, in your case, you don't have to worry since you didn't...hang in there....I think everything is fine especially since the HB was there.
PS-My LMP was June 16. I also got a positive on July 12 and my chart shows I ovulated on June 28, although I think it was more like June 29. And I'm 8w0. How are you already 8w4 if you conceived June 29?