Lag (Blocks loading at a very slow pace)

For some reason, I've been lagging severely in Minecraft. I have no idea why and I've been trying to resolve this by trying to change my game settings. Heck, I'm not even sure that it is bug or not... I haven't had any problems like this since Snapshot 14w29c. I'm Not talking about the block updating issue by the way. It is nothing like that.