Can't upload image into blog post

I have previously inserted images in many of my posts but in the last month I can not do this. I select the image from my desktop it is a .jog file (photo of staff member) it is 19.8gb, it them looks as if the photo is being uploaded to the gallery but a thumbnail does not appear, I get a blue cross instead and no image. I upgraded to the lastest version today but this has not helped. I have tried on Chrome & IE but it doesn’t seem to make a difference. Any idea’s??