Between Webster's Second International, (over 238,000 words), and the Scrabble dictionary, I only find three:
yex
yox
yunx
Yex
Yex
show
Yex
Windex
Jinx
xerographically
jinx
Xi
firefox
sex, suffix Six
Nissan 240SX?? lol
ex... EVERYONE KNOWS THAT!
earthquake words that start with x
No They Dont Start With "X"
doux means soft in French