subDomain = page of subDomiain (user) only

hii guys, i have some problem with WPMU installed on my server.

example: i have main domain at https://www.xxxxx.com and then, when user registered on my main domain, these user have user.xxxxx.com URL address. but, when i goto user.xxxxx.com page, the pages its same when i goto user1.xxxxx.com or https://www.xxxx.com or user2.xxxx.com

how to make every sub domain just display these user post when i goto user subdomain….?? not same for all user/subdomain displayed.

thanks