Overthinking is the biggest cause of depression. More you think, more you get depressed, so you really should get some help for depression. You should find the actual source/reason for your depression. Once you would come to know the cause, you are able to get rid of it. Best way tell your parents or friends about the things that affects you in your life instead of being calm, let them know how you feel so that whatever they think about you that’s not happened. It really help you out from this.