5wks 5days Unexplained Bleeding


I am pregnant with fraternal twins due to transferring 2 5AA blasts thru IVf on 1/19/16. My betas are as follows:
9dp5dt - 346
13dp5dt- 1800
15dp5dt - 4072
21dp5dt - 28519

This past Tuesday (21pd5dt) I stood up after getting my shoes on and had a gush of bright red blood. Panicked, I called my RE and they had be come in for a U/S and blood work. The US showed both gestional sacs had a yolk and beginning of a fetal pole which I was told was normal for being 5wk 4days. My cervix was tightly closed and I had no blood clots in my uterus. When I stood up after the vaginal scan I had a (tmi) stringy dark red thing fall out with more blood. They gently did another scan and everything was closed and still intact. So they sent me home with no explanation. I had some more stringy dark red clots come out and then I Stopped bleeding. All in all, the bleeding episode lasted 4 hrs. Later that day, they called me with my blood work for and my beta more than doubled perfectly to 28,519 and my progesterone was at 41 and estrogen was great (can’t remember the number) . I go back in for a scan tomorrow (6wks1 day) to check on heartbeats. Has anyone experienced this? Could I have lost one of the babies?