If you had a positive on a pregnancy test then chances are you are pregnant. They rarely produce false positives. The morning after pill only works within a very short time frame from having intercourse, so at this point it would not prevent the pregnancy from continuing, but could do harm to the developing fetus. I agree with Spade. You need to see a Dr. to confirm if you are pregnant, and to discuss your options if you are.
You can not trick your body into producing HCG which is the pregnancy hormone that is detected on a HPT.
I am a little confused - were you trying to get pregnant or is this something unexpected and unwanted?
Please make an appointment with your doctor and discuss all your concerns/fears with them.