I can't delete video that are labeled "from my computer"

So about a couple months ago I transferred a couple of videos from my computer to my iphone and now I want to delete them but I can't at all... I tryed to look it up and I went to itunes clicked on the iphone icon and went to photos to try to delete but the problem is I can't find on their... I'm not sure how I can delete it if it's not there. If anyone can please help me out that would be great I've trying to find a solution for months now! Thank you in advance