photos not in my camera roll

I went to a concert last night and I got home to find over half of my photos and videos i took aren’t in my camera roll. I have icloud photos switched on but the missing photos aren’t on my mac either. Some of the photos are grey boxes, when i click on one it shows up and i can watch the video (this isn’t just for the concert photos, there are now other photos in my camera roll like this). But on the other grey concert videos it stays grey when i click on them and i can’t see the video. i have an iphone 6s + on ios 12.1.4 if that helps. how do i get my photos and videos back?! :(