hotbar slot changes frequently on its own

im not sure how to reproduce this bug, it comes on its own, but my hotbar slot changes automatically. if im trying to eat, the slot will go to a weapon or lava bucket or something other than what I wanted to use. I usually play on servers, and during a hunger games fight sometimes my weapon slot will switch to a food or random item that I don't want to use. please help, this is affecting my playing a lot.