Thanks for the query.
levels above 25 usually indicates pregnancy
So according to your description you might have had miscarriage
The blood clot you noticed could be products of conception.
May be because of that your ultrasound
didn't detect anything.
The spotting you are having can subside soon.
For more details you can ask me through: http://www.healthcaremagic.com/doctors/dr-sree-gouri-sr/63429