My fiance is a recovering drug addict of 7 years, could his use of hard drugs cause infertility if we are trying to conceive?

Infertility possible: There is a simple test to answer the question of male infertility: get a semen (sperm) analysis for fertility (not post surgery). His primary care doctor can order the test and 'give peace of mind'.

Possibly: I recommend strongly that he get a semen analysis done as soon as you decide to try conceiving. There are way too many variables to say he 'does' or 'doesn't' have a fertility problem, the numbers on a reliable sa will get directly to the answer. I also assume and hope, for both of your sake's and a baby's, you are talking about a partner who is no longer using.