((hugs)) I hope you get good news on Monday.
I am no expert, but I think I have heard that it is normal not to be able to see the heartbeat on scans before about 7 or 8 weeks - just because it's difficult to detect? Maybe someone else might know more about this.
And of course, we've all heard stories of bleeding in early pregnancy that have happy endings.
This must be really tough for you right now - I'm not trying to downplay your concerns - just trying to give you some hope that things could still be ok.
Good luck!