multiple dragons, game crashing, stuff disappearing too soon

i finally found a portal, started working my way to beating the dragon, but the game would randomly start crashing "due to an error" and now, whenever I go back, there's two or even three dragons. I stay there for a while, trying to find my stuff from when I died before a game crash, but now when I go back, that stuff has disappeared, even though it shouldn't have been long enough for them to disappear. After a while the game crashes again. Minecraft is currently unplayable for me because of the crashes.