Macbook 13" retina trackpad stuck
In case anyone else is having the same problem out there, this may not be the best solution but it worked for me. 
My trackpad had been clicking just fine anywhere on it. Suddenly it would only press down in the left bottom corner.
I simply, closed the laptop,  flipped it over and slapped it hard in corresponding area where the trackpad is. I also lightly tapped it on all sides on a soft surface (my couch). Sure enough that did it. Been fine since for over a year now.
I guess something must have been stuck underneath it.