Rather than use the for loop that James identified as the problem, keep a global int variable x (give it a proper name) that you use to tell you which message to send. When you notice a button press, send the xth message, increment x and if it's too big, set it back to zero.
Perhaps twitter.wait already deals with this, but your code checks for the button being pressed - even with the suggested change it may send multiple messages per press because the arduino is fast and checks again before you can get your finger off the button. It's usually better in such cases to check for transition instead. Search the forum for prevbuttonstate or lastbuttonstate - they're commonly used names in transition example code. Debounce would be another thing to search for too.