Minecraft worlds loading extremely slow

This is a MASSIVE bug. The most noticeable effects of this bug are as follows:

Minecraft Worlds Loading EXTREMELY slow:

•It takes around 15-20 minutes to launch a world, the screen gets stuck on “Generating World” displaying “Building Terrain” with the loading bar a little over halfway. The beta information like the FPS and Mem update normally while everything else is frozen.

•It takes around 3-5 minutes to load any terrain (terrain I have already loaded before). While it’s loading items don’t show up if I drop them or break a block.

•It can take anywhere from 1-20 minutes to save and quit.

Random entity teleportation:

•In my world I’m in the process of making a castle, when I finally launched the world I found that random entities from my old base were teleported near me, not even to me, just near me. These were things such as a boat, several sheep from my farm (At my old base), a donkey (That was like 50 blocks away from me in a pen), a villager (I have NO idea where he came from seeing as I have no villagers at my base), and two hopper minecarts (probably also from my old base).

 

This is a MASSIVE BUG and essentially prohibits me from playing.