I just bought my 12 string guitar and the g,b and high e string go out of tune when i play it around the 8th fret i'm really getting worried. I'm wondering if its a problem with the type of strings it has
It's all but impossible to play 12 strings in tune. The problem is usually the intonation. Each string needs to be a subtly different length - even on a humble 6 string, you'll notice each saddle is placed differently. That's easy on an electric, solved by having 6 separate saddles. Even acoustics get round this by having a sort of slanting bridge.
Problem's caused by the gauge of each string differing. With 12 strings, the top two pairs are o.k., as they're the same gauge, but the 3rd strings are rather different, and a compromise is used, that's often exacerbated further up the neck, as they get more and more out with each other.
Of course, it may just be that it's been set up for one gauge of strings, and those were changed with no re-set up.
I recently learned that if your tuner key is loose, it will affect tuning. It can be tightened and therefore the string will stay in tune longer.
Usually the guitarneck gets bent because of the strength of the strings:. "If your string and sixth fret form a gap larger than 1/64th of a inch (.4 mm), the neck is warped. Hold the sixth string at the first fret and slowly slide down the fretboard with your other hand. As you slide down the frets, if the gap at your sixth fret decreases, the neck is warped and will need to be straightened."