Yes.
You have Zoom turned on.
Go to System Preferences->Universal Access and turn it off.
You might also want to check the options and turn off “Use scroll wheel …”
Sounds to me like you’re resting one finger on the mouse pad (thumb?) while using another finger to move around, which will perform all the behaviors you describe.
This is By Design and a feature I love for surfing. Hold your right thumb on the mousepad and scroll your index finger up and down = scroll the page up and down w/o having use arrow keys / position the mouse on the scrollbar. Very handy.