fairytale007 is absolutely correct. some women never experience an inny-turned-outie belly button during their pregnancies. so don't be worried. you're actually one of the lucky ones.
also, some women who started with an inny, end up with an outie even after the birth of their child. their belly button, for whatever reason, doesn't go back in. it's really weird.
i'm 25 weeks & 3 days pregnant & my belly button has just recently started to pop out. it looks funny right now because i'm a half-outie, and half-flat. i can't say inny at all because my belly button has blended with the rest of my skin.