My husband and i have been trying to have a baby. i'm o negative and he's o positive. is this a reason why we haven't been able to conceive?

Unlikely: That combination has led to thousands of successful pregnancies in the past & will in the future. The blood group issue has been reduced for the fetus by proper prenatal care for 4+ decades. I would not assume it to be the main issue. If you have tried for a year with no success it is time for both parents to have fertility studies done.

No: Your blood groups are not the reason for not getting pregnant. It would be prudent to see an obstetrician for advice. Take pre-natal vitamins. Wish you good health and a healthy baby!