Originally Posted by: BammBamm22but when i try to go to a differerent scale/key i get confused when it comes to adding the dominant 7 ...

I covered Triadic Harmony (building chords from the notes of a scale) in depth in this music theory tutorial:

http://www.guitartricks.com/tutorial.php?input=495

I covered major 7th, minor 7th & dominant 7th chords in these tutorials:

http://www.guitartricks.com/tutorial.php?input=501
http://www.guitartricks.com/tutorial.php?input=479
http://www.guitartricks.com/tutorial.php?input=499

http://www.guitartricks.com/tutorial.php?input=513
http://www.guitartricks.com/tutorial.php?input=961

I cover all this in depth in my instructor forum also!