MySQL Help, PHP and Database help

Hello,
I am building a form/blog/personal site for a small company. I was wondering if someone could help me in setting up my database. i have thought of a few options but i am not quite sure what one is the best.

each user have a person page, they need all their information stored, mail, bulletins, friends, etc.

i have my MySQL server setup as such:
SCHEMA(users) -> TABLE(Username) -> COLUMNS(disname, email, mail_from, bulletin_from, etc.)
The problem i am having with this is when send a new email or bulletin it adds a new row leaving NULL spaces.

For example:
Friends---------mail_message-----bulletin_message
Bob-------------null-------------------null
Tom------------null-------------------null
Joe-------------null--------------------null
null-------------Hello this is...----- null
null-------------My name is...----- null
null-------------null-------------------This is a bullet...
null-------------Hello this is...------null


see how everytime i post a new message or add a friend or post a bulletin it drops it down a row instead of filling in the NULL space. i dont like this and i beleive its slowing my server down a bit.

My other idea was to setup MySQL server such as:
SCHEMA(Username) --> TABLE(Mail, Bulletins, UserData, etc.) --> COLUMNS(Data)
idk how well this works and if it slows down my server any when i try to access multiple SCHEMAs at once.

Please can someone help me and aid me twards a better solution :)

Thanks,
DV6500