Do not ever, ever, put in other mods in already existing modpacks. Recently I tried playing Tekkit on my laptop. I decided to try and put optifine in to reduce some lag. It didn't work that well, but it still worked nevertheless. Then, I started seeing..weird things. I went to my inventory and saw my skin like this: http://prnt.sc/b6vels and I have no idea why. I played a bit more and I got tired, so I decided to close the game. When I was about to quit minecraft, I saw a bunch of images of the same thing just randomly placed. Sadly, you can't screenshot at the main menu, but I think that's for the best. Anyway, lesson learned: NEVER PLACE MODS IN OTHER MODPACKS THAT AREN'T YOURS.