I load up my game, it takes awhile (due to the amount of mods), but it always loads to the main menu. I can create a new world, but I am only able to play on it for a few minutes at most before a crash happens. Once I reboot Minecraft I cannot connect to that world, but again can make a new one, and it repeats the process. I've left the crash report below, if you need anything else, just let me know. Thanks so much for helping, it means a lot!
Crash Report (had to give a link, it said it was too long):
http://pastebin.com/r7sPdS2Y