automatically snaps to perpendicular from line

Just installed 2015 from 2013 and I've noticed it's started automatically snapping me to a perpendicular path after I draw a line. It's like I've got Polar Tracking turned on and set to 90 degrees. Is there a way to turn this off, it's massively annoying. Also very hard to search forums for when you don't know what it's called.

Thanks