I realize this is no help or comfort, but is it possible that you had an early undetected miscarriage? I have not heard anything about false positive pregnancy test results with Crohn's. If you have a link to information on this, I would be very interested in reading it though.
Good luck to you.
Diagnosed with Crohn's disease 11/05
SCD since 12/05
Asacol 12 x 400mg per day
fish oil, green tea extract, bee propolis, coconut oil, ginger