On my Twitter wall there are some tweets I never wrote

On my Twitter wall there are some tweets I never wrote

They are in the form of a short reply to myself.

The content of the tweets are always like this:

I am in! iups
or
Invite friends! gaul
or
Financial advise! phmj
or
So nice!
or
Awesome!

Why does this happen and how to avoid this in the future?