Help with downloading pictures...

Hello,

I have always been an iPhone user (currently owning a 5s with iOS 8.3) and have always uploaded my pictures and videos to my laptop by connecting my phone, via USB cord, to my computer (using windows 8), clicking on the internal storage icon, followed by the DCIM icon, and then copying the individual files from there. Recently, I tried to do just this and when I was done, I noticed that there were about 500 pictures that never showed up in the files. I tried restarting my phone, restarting my laptop, and reestablishing the connection between the two, all to no avail. I waited a couple days, hoping that there was just a glitch in the system, however, when I tried it again today, the same thing occurred. And the weirdest thing about it all is that it is random pictures that aren't showing. For example, out of pictures 1, 2, 3, 4, 5, 6, 7, 8, & 9 that show up on my phone, pictures 1, 2, 4, 5, 7, & 9 show up in files (and have been downloaded) although 3, 6, & 8 are completely missing and appear as though they never even existed. Is there any way that there is a simple fix for this and if so, what is it? I also even tried finding the pictures on the iCloud website, connecting my phone while it was unlocked, and by importing them by searching my computer (tips which I have seen other user ask about on this site) all with no luck 😟

Please someone help me =[