Crystal I hope you have had some more news from your Dr as to what is going on. With my last pregnancy my levels went down every so slightly and then increased but where not increasing at the rate they should have being. Turned out I had an ectopic pregnancy.
Yes the Dr is right. The levels should be increasing and the fact they haven't increased unfortunately isn't a good sign. I for you that you have lost a twin which explains why the levels haven't increased and the bleeding and your third BT shows a good increase.
Welcome to BB by the way.