This is precisely what we call an emergency or crisis around here.
I'd suggest you see your doctor again as soon as possible if you are unsure how far along you are; a simple ultrasound scan would help the doctor figure out just how far along you are. Time is of the essence here, so we're talking tomorrow or within the next week. If the doctor used a doppler and did not find a heartbeat, it is unlikely you are very far along, as dopplers can find heartbeats in the first trimester.
The decision to abort is yours and yours alone. There are threads for women who have had abortions that you can read; also, there are articles about abortion on the main site.
There is a Support Groups thread here: http://www.scarleteen.com/forum/Forum9/HTML/000004.html
and an article here, to get you started: http://www.scarleteen.com/reproduction/abortion.html
You can also find many voices of experience - adoption, abortion, parenthood - over at GirlMom.
Regardless of what you decide, the decision is yours and any decision you feel comfortable making will be the right decision for you.
Good luck to you, and don't hesitate to come back if you need more help and support.
[This message has been edited by Aria51 (edited 06-06-2003).]