Big genttle hugs hun. Im sorry you're going through this.
Bubs heartrate sounds perfect, DS was 163bpm or something around that stage, so try not to stress about that.
That doctor is a moron. Its not an implantation bleed. That happens after implantation. it could be breakthrough bleeding (bleeding around the time period is due due to hormones) or as the others said, a subchronic heamatoma.

Even though your doctor is booked out til Wed I would ring them, explain whats going on and ask them to squeeze you in. They usually keep a couple of emergency appointments free.

Maybe, try not to stress (yeah, right ) its more than likely fine. The fact that you saw a heartbeat and are spot on for dates is a great sign.