URGENT PLS RESPOND!!

I woke up perfectly fine went to restroom took dog downstairs to eat, five mins later hoped in shower and a gush of blood came out, check baby heartbeat with Doppler it was beating but still couldn't stop bleeding. Finally got to ER. A hour later she did Pap smear and noticed it went from heavy red to old blood. Checked my baby hearbeat 165 everything is fine, placement is fine, fluid fine, placenta fine.. HCG Is fine but they don't know why I was bleeding they told me this could happen. I did have a wet prep Monday at my doctors appt for BV/ STD testing and I was very rough I was cramping after for a good 15-20 mins but why would I just now bleed two days later. I'm worried this will happen again but doctors at ER says everything is fine. Has this happened to someone before?

FAST FORWARD almost six days later I’ve had brown discharge since then no heavy bleeding or anything but I keep having cervical mucus I can’t tell if these are old blood blots or my cervical mucus old blood, has this happened to anyone before my doctors office is not being supportive all they want to do is check fetal tones when I want answers. I have Doppler so my baby heart is beating, no cramps NOTHING. but my ultrasound came back fine I just don’t know why I still keep having brown discharge.