Super worried - hcg low and only slow rise

My hcg between Tues and Thurs last week went from 94 to 175. Because it was so low, had it tested again today (Tues) and it was only 340. By my calculations I should be about 5 1/2 weeks. My progesterone was only 9.4 last Tues, was prescribed progesterone suppositories, went up to 17.5 Thurs and is back down to 11 today (haven't missed any doses).

Feeling very sad right now (44 y.o. and 1st time pregnant). I actually woke up on Saturday and just didn't feel pregnant anymore (despite the crazy sore boobs and constant peeing). I kinda expected bad numbers today.

Nurse kept saying I probably ovulated late - told her it was pretty much impossible. LMP was May 26, bbt temp spike was on June 10th and haven't had intercourse since June 11th, so I'm almost 3 weeks gestation (5 weeks pregnant) at the very minimum.

Have u/s tomorrow morning and trying to stay positive, but I'm thinking they will find a blighted ovum. Trying to make it thru the day at work before I break down crying in disappointment.