Frustrating Border Padding Ugh!

Hello all,
my website https://www.alexcollierwork.com is running twenty-fifteen. I did some haphazard changes to the code, and I almost have it where I want it, but one thing! I can’t, for the life of me, make it so the left hand border is never padded.

There seems to be some type of dynamic resizing, when you shrink the window everything is fine, but on full screen mode the left hand border is padded, somewhat centering the content. I want the left hand border (the empty space between the left side of the window and the page titles to dissapear, and have the page titles ‘locked’ to the side of the window.

Can anyone please help??? Thanks.