Dropping hcg, told of a miscarriage, but still no bleeding?


I found out I was pregnant on Sept 18th. I went to the Dr on September 20th for blood draws. My initial hcg was 72. I had a redraw the 25th and hcg was 66. Then redraw again on the 27th and it was 46. I also had a transvaginal ultrasound on the 27th that just showed a gestational sac, it was done to rule out ectopic, since I have a history of ruptured ectopic. Have to go and have labs redraw on Friday. I guess my question is does anyone have any experience of when I should expect bleeding? My Hcg is still high enough to show on a pregnancy test.