Unexplained damage

While exploring I randomly receive damage, it has only been a couple hearts almost as if I was attacked or got fall damage but it happens during the day while I am just running across flat ground, nothing around to attack me. Today I jumped my horse over a fence, only a 2 block jump, and I died from fall damage. I had full health and shouldn't of received any fall damage but when I respawned I was at original spawn point, not my saved spawn point, and the whole world was very slow to generate like I was standing in the void.