What does it mean to overthink things?
Maybe you're uncertain about things in your life at the moment and maybe you've just got a lot of things going on. You have to try and relax you'll only end up making yourself sick with all the thinking, believe me I know...I always think too much and usually I end up getting depressed but I have learnd to deal with it... sometimes by getting involved in different activities...and looking at whats important in life and the positive side of things...Its also good sometimes to write down all the things you are thinking and start eliminating them one by one, by doing something to reach a result!
You think so much your head hurts.
You think to the point where you can't find a definite answer.
You make the idea a more complicated concept than it really is.