Suddenly, page is too wide for browser (desktop and mobile)

Site URL: http://hilarybeckwith.com/

I've been fine-tuning some image sizing and fonts recently (may be unrelated?), and am now starting to see that on desktop, AND mobile, my site scrolls to blank space to the right, as if it is too large for the browsers.

Can anyone please help me pinpoint what is causing this, and tell me how to fix it?

Do you use any custom code? Try checking all.

Or Try adding to Design > Custom CSS

html, body {
    overflow-x: hidden;
}