Crashes

My Minecraft is not working as it should. I havent layed since 2015 and it use to work well, bt now its going slow and i cant move freely (basically its like if it was crashing all the time). I cant do anything and it says to reload the world or something. I cnt move my mouse freely, like for example i cant look behind, i have to move my mouse many, many times to the left or right to do so.