You may want to inspect how exactly you are exporting your photo from your photo editing application. It does not necessarily have to be a huge file as there is a maximum width and height.
For example facebook.com/facebook page
Layout: 280 x 280
Size: 6,997 bytes
Though there are only three colours used here.
So you many want to also check how many colours you are using.
In the past (very long time), I used to have trouble uploading transparent PNG files, so I would recommend staying with JPG and make sure your program is set to optimize for web viewing. Maybe try uploading the original photo first. Also ensure your resolution is around 72 ppi.