my best friend?

im best friends with my best friend for 11 years... suddenly i cant talk to her anymore like i usually did..
she feels like a stranger to me sometimes... then i think why do you aks me how i am??? i dont want to tell
you... But the thing is i just cant tell her... and she never asks whats wrong... or never see´s if somethings wrong... its have been realy bothering me...that im feeling this way about her..
just ONE question... did you ever had the same problem and how did you fixed it????????
xo THANKS <3