im not 100% sure what you mean by blood in the uterus, because the lining of the uterus (what comes out in your period each month) is "blood", but im assuming its not that
what is the doc doing? is he gonna keep a closer eye on you or do more ultrasounds or something? id hope so, honestly i dont know anything about what your talking about, i wish i could help you more, maybe talk to your doctor tell him you are really concerned and maybe he can do something to put your mond at ease
good luck, i hope its nothing serious and you get to have a wonderful 9 months