blood clotting behind the placenta

i am 17 years old and i have my first prgnancy i am 8 weeks...i went to the ER do to stomach pains and cramping..they told my i had an placental abruption...the next morning i find out that it is not that according to my ob dr... he says it is blood clotting behind the placena sack and i was wondering is this can pass and correct its self and what are the chances of my being able to have my child?? i dnt want to have a miscarriage and i want to know if there is nything i can do to stop or fix this or what are the odds of us being okay in this situation i have no external bleeding and my ob says thats good but i not to sure i just need help is anyone can help and give me the best advise i would be most greatfull thank you for the help always,
                                                                        joanna