Either your mom or your dad had to be a carrier for you to be a carrier I thought - unless it is some quirky genetic mutation (not a geneticist so I don't know if that is even possible).
I do believe that since your husband is not, that means your babies have a chance of being a carrier but would not actually have it. That's how I understood it when the whole screening/testing thing was explained to me, but it turned out neither I nor my husband were carriers, and we were only tested during my first pregnancy so I'm not sure if I am remembering clearly.
Do you have a genetic counselor you can talk to? Or maybe just call back into your OB to get some clarification?
I had the same situation as you. I am a carrier and my husband is not, meaning that our baby will have a 25% of being a carrier, 0% of having CF though. I know my mom is not a carrier because she tested negative the last time she was pregnant, so it just leaving my dad. He must be a carrier as well but since my mom tested negative, he never had to test and never knew.