Dates not adding up..

Someone please put my mind at ease.. I am struggling.

I got my BFP (vfl) on August 20th, LMP started on July 25th.

I have a very regular cycle, always have. I just had a baby Feb of this year and got my period exactly 1 month after the bleeding from birth stopped and it’s been regular ever since.

We had our first appt at 7w6d and my doctor said the pregnancy looks more like 6w1d. Also he could not find a heart beat (vaginal US) and the baby did not have visible limbs. Just a ball.

To me this doesn’t add up.. when I got my BFP I was 3w5d according to LMP. If the doctor is right about dating then I would’ve been ovulating around time of BFP, so it wouldn’t have been possible for me to get a positive.

I’ve had stomach (not lower abdomen) cramps and diarrhea for a week straight.

I’ve still had morning sickness and food aversions and I still feel “pregnant.” I’ve had zero bleeding.

Obviously I’m worried about an M-word since the baby looked smaller than an almost 8w baby with a vaginal ultrasound. And he couldn’t find a heartbeat. And I’ve had this weird cramping/diarrhea.

I took an hpt a couple days ago and the test line was darker than the control line so I’m hoping that means my HCG hasn’t gone down.

We don’t go back for our next US until October 3rd.

Someone please reassure me if you’ve been through something similar or just have general insight! 🙏🏻🙏🏻🙏🏻🙏🏻🙏🏻💙

Thank you in advance 💙