No, at 7 1/2 months you would test positive for antibodies regardless of Crohn's or the medication you're taking if the virus was present.
Trinity
Immunocompromised individuals can experience delayed seroconversion of HCV antibodies. I’m personally unfamiliar with Chron’s; the rate of percutaneous needlestick transmission for HCV among health care workers is low, however:
Needle stick Risk for Occupational Transmission of HCV
HCV is not transmitted efficiently through occupational exposures to blood. The average incidence of anti-HCV seroconversion after accidental percutaneous exposure from an HCV-positive source is 1.8% (range: 0%--7%) (73--76), with one study indicating that transmission occurred only from hollow-bore needles compared with other sharps (75).
http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5011a1.htm
--Bill