man i've been trying to find a song for sooooooooo freekin long
its not it all the ova's i have and i dont understand why
its the one for example on the episode 26

http://anime-media.com/darker-than-black-episode-26-ova/

starts at 18.30 on the dot and gets to its peak, which is also the part i love, at 19.10

help me out plz :(

You have to realize that there are some tracks for this anime that were never released (so far). I believe that there were only 3 osts released so far for this anime. The ost for the 1st season, the ost for the 2nd season, and the blu-ray release ost that comes with the DvD (which includes some new releases).
Frankly, I want the song found in Episode 20 of the first season during the confrontation between Hei and Alma, to my dismay, I never found the beautiful piece of music in any of the released osts. ='(
The best choice is to wait and hope for a release.
I've noticed that this phenomena also occurred with the anime Ghost in the Shell: Stand Alone Complex. In both of these cases, the majority of the OSTs were composed by Kanno Youko. That might help to explain why some tracks are not released.