So you 'look' innocent? For appearance I'd say...keep that 3day beard on and you'll feel more manly
As for the mindset...learn to program your automatic (subconscious) behavior. What I'm saying? When you have certain thoughts and/or feelings, first learn to notice them, then learn to see what they're doing and finally learn to alter them to get you into the right attitude and/or mood.
Let's go way back and look at the mistakes most guys make. I.e. touching your face unnecessarily while talking to a woman. In order to stop this behavior you need to notice when you're doing it. (Hey I'm touching my face!) You notice it and stop doing it and place your hand into a more relaxed spot. Repeating this will change the way your subconscious mind works and you'll stop touching your face eventually.
Same thing goes for your innocent nice guy behavior. When you notice you're being soft again, change your thought pattern and maybe say something cocky. It might not get the best response and maybe it will, but It'll help you to start behaving that way naturally.