No, you can't be "a little bit pregnant." Either a zygote has implanted itself into your uterine lining or it hasn't.*
It's like so-called agnostics. You can't just be agnostic, no matter how much you want to get out of calling yourself an atheist because you don't want people to think you worship Satan and eat babies. You're either an agnostic atheist (you don't know if there's a god but you don't believe) or an agnostic theist (you don't know if there's a god but you believe anyway). But either way you have an opinion, and that opinion makes you one or the other. It is impossible to neither have belief nor lack belief. If you're really not sure, well, that's not belief now is it? In other words, you're an atheist. A "weak" atheist, certainly, but an atheist none the less. Calling yourself an agnostic doesn't change that.
Embrace your atheism, join us, help us rule the world. And eat babies. They're totally yum.
*I don't count having a non-implanted zygote floating around in there as "pregnant," since most of them are naturally aborted, but if you do then replace "zygote has implanted in your uterine lining" with "sperm has fertilized one of your eggs," shake well, and enjoy.