As everyone else said, There is nothing wrong with the way you feel about your step-dad, WT.
I think you just feel more inclined to your step-father because you've grown to him more than your biological father. I'm going to assume you've spent much more time with your step-father ever since your mother and father split. It's natural to feel that way if that's the case - it's that you've become more closer with your step-father because you've gotten the chance to establish a deep relationship with him while it was your biological father's choice to distance himself with you and your mother.
But if you truly think it's awkward, maybe you should open yourself to your father and try spending sometime with him instead of being in your room when you see him.
Either way, none of this is wrong. Regardless of the rank/title in your family, it's okay to feel that way about your step-father.