hello, I'm sure this has been asked before, but I'm kinda in a pinch. But first off, I have no problem barring any form of the A chords, but I do have problem barring 6 string chords where only 2 frets are fretted, such Em and E7 barre forms.

I always can't seem to barre the D and G string. I know I'm suppose to use the sides of my index, but I think its because my fingers are kinda slim, causing there to be a some kind of dent between my bone joints, making it difficult to barre..

I know practice make perfect, but I need soem kind of advise on how to practise
I was in your position when I was just starting out not too long ago. There isn't really any advice I can give you because it just comes with time as you build finger strength. Good luck!
ya your fingers will be sore, so when they are just give it a rest because you will only get frustrated and when you come back to it you will be a bit better, just be patient, it takes time, but it is possible that the action on your guitar is very high which would make things dificult
Just keep doing whatever sounds ok when you barre it and stop what sounds bad... heh that's about as good advice I can give... Just keep trying, it will eventually come if given the opportunity.
well start on electric, cos it's easier than acoustic

i remember what i used to do was not actually strumming, but just holding the chord shape, doing so longer and longer as it felt more confortable, this helped me build finger strength
First of all, what's the gauge of the string are you using? And second, is your guitar tuned to the "proper tension?". Some players are unaware that their guitar are tuned way up further than the proper tension.

If these contribute to some of your problems, I'd suggest using a light-gaged string, something that starts from .009 as the first string. Then tune your guitar a half step lower than the standard tuning (Eb tuning) for practice purposes.

Hope these can help you out.
+1 on what everyone else has said.

Also, make sure your guitar is properly set-up. Your instructor, or a friend who's been playing for a while might be able to tell you if it is or not. If the strings are a milee off the fret board, barre chords will be more difficult.

My advice is to squeeze your finger against the fret like your squeezing toothpaste out of the tube. That way, you have another plane to push against, pitting your finger into a 90 degree angle formed by the fret and fretboard.

Try these chords up and down the neck. If you find a spot that feels a little better for you, start there and really get them perfect. Then begin moving up and down from that position into new territory.

Oh, and practice....a lot. There's no substitute. Guys like Vai and Malmsteen have been known to practice ten hours a day or more. I know the six or seven I've been putting in lately has REALLY helped my playing.