I have really fat cheeks, so I used to walk around with them sucked in. I also used to walk and sit in an exaggerated 'alpha', unmoving fashion.

Today, I tried to relax everything. I let my cheeks droop naturally, and sat and moved however I wanted. This led to a huge change in my confidence, and the reception from girls. Probably because subconsciously, relaxing meant I didn't care about how others perceived me.

Try it out, especially if you tense your face all the time.