PCB designed in Fritzing shorts almost all pads... is it the copper fill?

Hi Everyone-
Newbie here. I made this very basic PCB in Fritzing and had 3 made by OSH Park.
I mounted my micro-controller onto it and realized that it shorted out. When I tried to troubleshoot with my multimeter, I discovered that every pad that has a trace is connected to ground. This is my first PCB design and I am just trying to learn by reading articles and trial and error. Since all of my other PCBs are hand wired, I have never used copper fill and I wonder if the copper fill in my design (automatically generated by Fritzing) is the culprit or if anyone has any other ideas as to what the problem could be. Here are images of my very simple PCB (top and bottom) -

I really appreciate any feedback. Thanks for reading.

I should also note that pads that are not connected to traces do not short out.