Unable to upload photos to my website

I have noticied that for over 12 months now I have had periodic times when I am unable to upload photos to my website. No error message. It just doesn’t happen. For example, I will create a new gallery and then select say 10 photos to upload. I click upload and only 2 photos are loaded. I scan the folder to see if the other images appear, and they do not. This has gone on for so long I have virtually accepted this problem. I am a fairly basic WordPress user but I am a quick study, show me how once and I can do it own my own.
Thank you!