Photos uploading to computer at a different size than original on sd card

I have a Toshiba Satellite C55t-A running Windows 10 Home. I am trying to transfer photos from my Samsung Galaxy S5. When I removed the SD card from the phone and tried transferring them from the card to the computer the system would freeze after a small number of photos were moved. After putting the SD card back in the phone I tried moving them using the usb cord and going to the DCIM folder, opening a picture with the windows photo gallery. It gives an option, in the edit, organize or share tab, to transfer photos in groups by dates. The problem is when I do this the photos are being transferred at an extremely small size, like 12.6kb instead of the 4.82MB. Can anyone give me any idea what the issue may be? Another issue is, if I try moving photos from the same time frame to the folder of the same date name it will download duplicates of the photos already there instead of telling me that a file with that name already exists. So I have maybe 13 photo's with two or three duplicates in the correct size and then all others are smaller. Any help is appreciated