Fish, let me tell you: I'm on 800mg of progesterone (pessaries) and I still bled, remember? Even after terrifically high beta results (remember? We thought it was twins?) I feared mt six-week scan enormously because of the brown sludge and then the bleed on the morning of the scan. Everything was fine. Since then I've had to befriend the sludge 'cos it aint going anywhere soon by the looks of it.
The Clearblue digis are not designed to be used frequently. They are not to be trusted to measure HcG properly after the first fortnight. Do not use another one.
I'm going to talk about God now: there is no need to fret about an embryo's ability to form thing like a heart. The embryo doesn't control this: God does. Whether you believe in Him or not you have to see that a higher power than the embryo itself is making its heart beat and limbs grow. Have faith that there is a Creator behind all this much bigger than you or the embryo.
Early scans and beta bloods only assuage our fears momentarily. We just become fretful about the next scan (like I am tomorrow) or the next test and it goes on and on ad nauseum. The answer, in my experience, is to look beyond your own human doubts and try to have faith that whoever or whatever designed you and your baby (and I believe that is God) is working out His plan with no effort required at all.
I know it's scary, but you have to put something in place to drive those demons out. They will tell you that this is all up to you and the embryo now and only fretting immeasurably will bring a happy outcome. Not true. This embryo's life does not depend on your frame of mind. Take courage and have faith xx
That goes for all of us 