I have started playing guitar at, what some might consider, a late age. I am 20 years old and i've been very dedicated for the past couple of months to teaching myself the guitar (with the aid of a few friends and about 6 or 7 odd lessons). I have learned most of the chords, I can find my way around the neck quite well and barre chords are now as swift as power chords to me. The one thing I can't get down are scales and improvisation. I simply don't know what sounds good together. Also of course my playing is a bit sloppy and inconsistent but I am sure that proficiency obviously comes with time. I am a bit worried that I could be pitch-deficient, although I have a very rigid and particular be it broad taste in music (those terms are contradicting, I know, but I do love all great music and I seek it out intensely)

whatever, my real question is: How can I comprehensively grasp scales. I can play all five of the pentatonic scales and the major scales across the fret board but I don't know how to put them together to improvise. I guess I may be talking about relative scales. But I don't understand the concept of relative scales, where can I read explicitly and comprehensively these details?

sorry, I'm long-winded