When you put your saddle on, start forward of the final spot and pull it back slowly. Your saddle should stop on it's own. That is the place the saddle is made to fit your horse. If it is too far forward then the saddle is improper.
A Western saddle is made to overlap the shoulder, not sit behind it as an English saddle does. A Western tree has a flair in the front which will allow the shoulder to move freely. Your rigging will be in proper place to fit into the girth area.
I don't think your saddle is too far forward, I think it may just be too small.