I take fall damage when I build up

So I was just in the nether minding my own business trying to get an achievement for killing a skeleton with a bow 50m away and as I was building up (full health by the way) I took fall damage from literally nothing at all and died. At first I didnt think much of it but when I went and got my stuff back I died again the exact same way over lava trying to get to my portal so I ended up losing all of my valuable items that I have been working hard to get over the course of 2 months but because of that bug those 2 months were wasted. I was so upset because of it
I ended up deleting the world because I didn't want to start again from scratch all because of a stupid bug. Please fix this soon.