Whenever I'm with a girl, casually or just texting, I really hate telling my friends who they are because I care way too much about what they will say. They aren't shy about saying the girls are ugly or whatever and so, it even causes me to meet girls in public only when its dark or in very private places. When i am with a girl and many people are around, usually the only thing on my mind is on who will see me.

For example, last night my friend noticed I was talking to someone. I wouldnt tell him her name because I was afraid he'd know her. He probably doesn't even care what she looks like. I'm 18 btw, so my friends range from 17-20.

I would be grateful if anyway could help me pin the problem so I know what is going on so I can be aware and work on fixing it. Thanks guys

Your friends are behaving like dicks... but then again, they are mostly teenagers... So you should work on your reaction to what they say... My reaction to this kind of juvenile behaviour was to joke about it, for example:

Friend: that chick you were making out with is pig ugly
Me: I have a fetish for ugly chicks
or
Me: making out with ugly chick trumps masturbating to youporn

Friend: are you a chubby chaser, man? that chick is huuuuge!
Me: yeap, it's a freudian thing, reminds me of my mom...
or
Me: as a matter of fact, I am... could you please introduce me to your mom? she's quite large herself...
or
Me: yeap, the bigger they are, the harder I get...

Thing is to not take yourself too seriously. When your friends notice that you are not bothered by their lame jokes, they will stop. And you should keep this in mind: when people talk about you, you have done something worth talking about.

Good luck!