A few friends of mine said I look like mess? But I don't want to follow any trends and such.. can you help me on some comebacks to say to them that I don't go for trends, and I don't want her to comment such things about me again? Please help! Not a rude comebacks, but a nice one indeed? Or sarcastic ones. Thank you.

Skip the come backs and just tell them upfront that you really like what you wear and that you would appreciate it if they no longer commented on your choices. You aren't dressing to impress them or anyone else.
If they continue, you might want to consider finding nicer friends.

Not following trends doesn't make you look like a mess.
First you should know why they told you that. Was is really because you do not dress like them or follow fashion trends? If yes, then ignore those, comebacks will only give them more chances to pick up on you, or you can just tell them straight in the face that you like your clothes, and you don't need their approval in any aspect. But, if they didn't talk about the trend, if there really is something wrong with your dressing styles (ask her clearly about this), then you should change.
There are two main types of reasons people tell you bad comments,
1. They want to annoy the hell out of you.
2. They want to help you improve.
Not every bad comment has the first meaning. You should understand the situation first.

Next time,tell them "I look the way I want to look".It's great that you create your own style instead of following trends and friends should not only respect that,but also,they should never put you down with unconstructive criticism that is only meant to make you hurt.I think even better than answering back is keeping that friend away and not giving them much attention,focus on people who at least try to give you constructive criticism!

Well to tell you the truth, why do they think this ? Is there issues for real with the way you dress and are they only trying to help you.

I watch a TV show, called "what not to wear" and to be honest there are people who think they look OK but they dress horrid. So before I would agree to tell them anything, I would want to be sure that I did not look a real mess

I would say, "what do you mean", and look at them with a quisical look, that says you are waiting for an explanation.

Then ignore all stammering and uncomfortable moments when they try to explain.

Laugh and make a huge joke out of it. "Yup, I'm a real Messy Bessy." And if they call you "Messy Bessy," with great cheer bestow upon each of them a nickname, such as "Crabby Kate" or "Mouthy Mike" or "Silly Cindy."

Say I like what I wear it's not bad it looks .o.k. to me