Help! Trackpad is bugging out

Try disabling "Tap To Click" in Trackpad settings in System Preferences...

 

May want to look at getting a new trackpad. But first, hold CMD R and see if the trackpad misbehaves while in the recovery partition. If it does you know it's hardware.

 

Yes. It will load a recovery partition where you can mouse around. If it runs fine there it is a software issue.

 

Good advice here. Just a note that trackpads seem to be sensitive to moisture. One or two rain drops and you can get a badly misbehaving trackpad. Sometimes they work well after they dry out for a few days, most of the time not. I forget, does the early 2011 MBP have a removable battery under the trackpad? A swelling battery can put pressure on the trackpad making it wonky.

 

It is removable, as in not attached to the top case like the rMBP models. However, Apple doesn't want you to remove the battery as it will void the warranty.

That being said, a new trackpad can be ordered from iFixit in new condition for $100 including screws. Now if the OP has AppleCare, it should be covered under that agreement.