Perhaps, it is the way you carry yourself.
We all try and size each other up first by appearance, then how we communicate nonverbally. The way you hold your head or touch your face and hair. The stance you take while sitting, standing. . . . Arm position, whether it be crossed, down by your side or simply somewhat guarded . . . Sitting while leaning in versus sitting while leaning back . . . The micro-gestures the face muscles make.
If we can in closer, the pheromones we give off introduce another attraction point.
All of these subtle ways of communication are going on and have been as we evolved. They are subconsciously sending signals to those men you meet, and for some reason they are not registering as "Possible Mate" to them . . .
Perhaps you have just not met the right guy who is attracted to these things about you as of yet. Be patient.