Can rabbits wait more than 6 months to mate?

I have two rabbits, do not know what they are, but I got both of them more than 6 months ago. I have not had any babies yet, one of the rabbits will sometimes try to get on top of the other one, and the other one refuses and has never showed any of the that type of behavior. Now, that one that was refusing all the time has made a fur nest in its hutch, is acting extremely aggressive(biting, nipping, scratching to get away) when you touch its stomach, and the seem to be big. Is it possible that my rabbits could have waited this long to have mated? Is my bunny pregnant?? Please help me!!