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I am a Muay Thai fighter,
Well, so much for pitching martial arts to improve your confidence!

I know the other guys gave you some razzing, that you can't be good looking if you're a fighter, but the briefest survey of the UFC or historical boxers will disprove that. Muhammad Ali was famous for teasing his opponents that he was the baddest, the prettiest.... Muay Thai is not a style that is usually subject to McDojo Syndrome, although Googling around I realize it's not impossible. I'm going to assume you have real fighting skill and don't have trouble taking an elbow to the face, except that well, it hurts. If I'm wrong, you be the judge of that and find a different school, but don't bother letting anyone else be the judge of that. It doesn't matter.
You can use what you've learned in battle to help you in other areas of your life. For instance, you know how to stand toe to toe with someone without any fear, or do something productive with your fear. You probably know the quietness of dealing with an opponent, the blankness of mind. Use those same skills of quieting yourself in the ring, and observing what is happening, when you are out trying to hit on women. I haven't spent time actually getting beat up myself, but I have spent a lot of time in the real world with people getting in my face, trying to run me off of property I have a right to be on, trying to intimidate me, trying to threaten violence, etc. I've been tested in the real world where there isn't a ring, there isn't a referee to intervene or keep things under control, where it's just their emotions vs. my emotions. I use the quietness to stand my ground. I don't rise to their anger. One of my sifus taught me a long time ago that it's my job to control my emotions, to let the other guy get all worked up, so that he gets overconfident and makes the mistakes.
Mind you, I also walk away from fights I don't need to have. Maybe that's part of your problem.
You feel you have to fight. You don't, actually. My own priority when confronted by somebody, is usually to keep that person from wasting my time. Court case is a waste of time, talking to police is a waste of time, his buddies trying to take vengeance later is a waste of time, not to mention that the emotional expense of getting my adrenaline all riled up is a waste of my time. Why should I have to feel like shit for the next 12 hours because some douchebag wants to put me in fight mode? I don't need it, I've got better things to do. I've also proven my ability to stand my ground many times in the real world, so I don't have so much to prove to myself anymore.
So, I will lie and play like a weakling if it'll get me out of the situation quickly. I don't care, my pride is not on the line. I am manipulating someone I consider to be a complete dufus, a person of low consciousness and moral character. I win by getting the result I want, by any sneaky means available. He doesn't need to know what I'd really do to him if I had to. I'm happy to play the part of a sniveling nerd, someone that they don't get any prestige points for beating up, if it makes the other guy go away.
Some kinds of people prey upon weakness though. If you show weakness, they take it as an invitation to dominate you. Being polite won't get them to leave you alone. They will fixate, bully, and try to take their personal demons out on you. To such people, I show strength. I use the calm. They run their mouths and get in my face. I just empty myself and prepare for the fight, I don't engage verbally anymore. I'm thinking about how close their ribcage is to my palm, how they are off-balance, how they have no combat discipline flailing their arms like a monkey trying to look impressive, etc.
Sometimes I will say something back to them. Some people hate you when you lie to them or try to duck them, and are surprisingly good natured when you stand up to them. It is a form of attention seeking on their part. They feel respected that they were taken seriously, and that someone actually reacted with some balls for a change. It is all judgment. I am good at sensing what another person actually wants to hear, where they actually want this to go. I do whatever it takes, whether it's displaying weakness, strength, saying nothing, or saying something forceful.
Try to apply this to your entire life.
You are a fighter; that means you don't have to fight. Use the quietness, the calm, to feel what's going on around you. Empty yourself.