Why won't my cart icon - on the header fit?

Hi all,

Bit of an annoying issue. The button in the top right of the header does not fit onto the header, it is off to the right, and means my webpage doesn’t fit on mobile phones or desktop sites without the user having to scroll right as it cuts off half the cart.

Image attached - essentially. How do I bring the button showing how many items users have in their cart to the left, so it does not expend the whole webpage?

Thanks for your help.

Still need help, please