My Minecraft is COMPLETELY broken. Please assist?!

I've been playing Minecraft on my pc for a few years now, but tonight I was playing 1.9, but I switched to forge 1.7 to try out a mod. When I got back to 1.9, it was chunk glitching ridiculously (Even my own character model is horribly glitched). I reset the video settings, restarted my pc, switched versions (optifine, 1.9.2, 1.9.4,) and still nothing. I only have a few weeks left of school and I would love to spend it playing Minecraft with my friends, so somebody Please Help!

Read more: My Minecraft is COMPLETELY broken. Please assist?!