Did you google "Facebook Shrunk" ?
Everything has shrunk on my FB page... fonts, pics, etc. | Facebook Help Community | Facebook
Check your browser Zoom settings--usually in the 'View' or 'Tools' menu on your browser toolbar. Standard setting is 100%--you can reset to 100% by pressing and
holding the CTRL key and press 0 (zero).
OR
Most computers support quick change keys: press and hold CTRL key and press - (minus) to reduce or CTRL + (plus) (SHIFT = ) to expand. [CMD instead of CTRL on MACs].
OR
Press and hold CTRL key and turn the scroll wheel on your mouse. One direction to enlarge, other direction to reduce.
Drawback is you may 'lose' the outside edges of your page if you enlarge over 100%.