Thanks for the query.
Don't worry passage of blood clots
may not always indicate dangerous problem.
But you have to get examined.
Consult your gynecologist once and take tablets to stop the bleeding first.
Then you can get examined and go for one ultrasound
to fins out the possible cause for your problem and take treatment accordingly.
For more details you can ask me through: http://www.healthcaremagic.com/doctors/dr-sree-gouri-sr/63429