perfectly imperfect's blog: "LIFE"

i was wondering if anyone knew if and how i can check if someone is jumping off my wireless.  for some odd reason it's saying i dont have the full 4-5 bars i should seeing as i'm only 15 ft frmo the router.  It used to show full connectivity which is why i'm assuming it's due to someone jumping on my internet.
Is there a way to tell?

if so, how?

and can i boot them off my internet?

thanks so much!!!!