When I talk with a girl

I am the youngest of three brothers in my family. My older brother is very handsome. He got married some years ago and he moved to Argentina with his wife and his daughter. My middle sister is so pretty. She is thirty now and she is still single. I wonder why? Ok, now is my turn, I am the youngest with a good personality.
When I was a small kid, I did not realize that I was a little different than my brothers. David is white, a tall guy and he has green eyes. My sister is also white and she has a beautiful face. But what about me? Well, I have a brown skin color and I am not so tall, though at least I have a nice smile. While I growing up I noticed that people had a preference in for my brothers, even our family looked seemedmore interested in they them.
It was a quite complicated for me to build confidence and having a good self-esteem. I wanted to get better grades than theythem . I wanted to be more polite than they them but even doing all this these things I couldn’t be happy.
I moved to another city because of college. I felt that I did not need to be competing with them anymore. It was great, it was fantastic but that made me feel alone.
I wake early in the morning to go the gym, I am doing the same thing for two years. This allows me to change my perspective and build confidence. I am 29 with a good profession now. I just had have had just two girlfriends in my entire life. I like pretty woman, I was dating with a beautiful girl. In fact, she won a beauty competition in her small town. Although, she is 22 I like her so much because she is so smart.
When I was younger I couldn’t approach to beautiful girls because of my lack of confidence. In college I had good friends as like many people make but my problem with girls was devastating me. Each time that I approached to a girl, I felt anxious and I messed it up.
I had been single for two years until Evelyn came into my life. I met her the last year but recently, we had been dating for a couple of weeks and when I heard that my best friend is going to get married, that made me feel anxious again because I am the only single in the group. I couldn’t handle my emotion. I was polite and I always made her laugh but I showed me to her full on (I think what you want to say here is 'I came on too strong'). I was afraid to be alone. I haven’t had news about her and I don’t judge her why.

Very well written. You are so close to writing near perfect English!