It sounds like you are just super early,
When was your last cycle?
Also some women do have bleeding it's more common than they let on. I bled a decent amount with my first and she's a happy healthy almost 2 year old.
I had a period with my first and it is looking like this one did the same.
Sounds like one is still growing my sister had it where one twin didn't grow early but second was all good and growing well sounds like that's happening. Fetid don't get a heart beat untill they are about 7-8 weeks depending on the fetus.
How far are you ?
Good luck for tomorrow
Let us no how you get on