Bi-curious??

OK so first off I know bi curious is usually someone who identifies as "straight" but is curious about being with someone of the same sex but I am currently the other way around.

I am in a same sex relationship but have recently noticed I have been thinking about being with someone of the opposite sex? What does this mean? I am currently with a girl but am wondering if my desires to be with a guy could just be linked to the fact that I want to be pregnant & have a baby so badly? Has anyone every experienced anything like this?