It sounds like you have a phobia.
Phobias are false perceptions of reality.
Your negative experience f*cked you up because you were young and still developing your sense of self and who you are.
Basically, your self-image.
Unfortunately, you unconciously programmed yourself to see yourself as a guy that women don't like or are not attracted to.
Dude, that was the friggin fourth grade!
Girls are insecure and silly at that stage.
Boys are insecure and silly at that stage.
The reality is that some girls will like you and some won't.
Not every girl is out to stomp on your heart just because you asked them out.
In fact, if you went up to 10 random women on the street and asked them for their phone number, on average only about 1 or maybe 2 will give you the time of day.
Even the ones that turn you down will usually not be rude or mean unless they are just nasty b*tchs to begin with.
At the most they'll tell you they have a boyfriend (true or not, it doesn't matter), they'll say they are in a hurry and can't talk, or at the worst you'll get a funny look or they'll just ignore you completely.
That is what happens about 99.99% of the time you approach a woman and get turned down.
None of that stuff will kill you and none of it changes who you are before you tried to speak to this girl.
If you get depressed or feel bad because some strange chick that you don't know from a hole in the wall and who doesn't know anything about you, tells you that she has a boyfriend or some other bullsh*t, then you need to develop a greater sense of yourself.
First off, when a woman rejects a man's advances, it isn't personal.
Do you genuinely have a good opinion of yourself as a person?
If you do, then that is what you focus on and not the imagined opinion of some skank in a tight dress.
(jk)