Question about the keyboard

[ilovemyphone]

So, i am noticing that some of the keys on the keyboard are making a sticking sound..like i would roll my finger on top of the key and it makes a sounds as if the keys were sticking..and if i would push the key in ( like typing out a text message) it makes a sound as if the keys were sticking..and no..the keyboard is perfectly clean..i think that possibly its just that they keys are worn out..