When I was reading your question I felt disheartened by the amount of sadness you’re experiencing. It’s always difficult to read the letters of individuals who are suffering so much. While it is always difficult to offer anyone an “official” diagnosis over the Internet you’ve provided enough information in your letter for me to know that you’re probably experiencing depression. Your sadness seems very genuine.
It’s important that you understand a few things about depression. Depression is not the result of weakness. People become depressed for various reasons none of which are the result of people being too weak to handle their own problems. Depression is not something that people bring on themselves or purposefully cause. Unfortunately there remains a stigma associated with depression.
The second thing that is important to understand about depression is that it’s very treatable. With the right therapist you could absolutely recover from depression. That’s why it is so important that you do not continue to keep this a secret. In your letter you stated that you believe your parents may think badly of you if they learned of your depression. If I were able to work with you in person I would examine what evidence you have to prove that your parents would think these negative things about you. I suspect that you actually have no evidence to prove this and that much of what you’re feeling is related to fear and your own ideas about depression. There is a very good chance that if you told your parents they would be open to getting you help. They would probably not think negatively of you nor would they consider you weak or believe that you’re overreacting. If you show them the letter that you wrote to me they may easily see that you’re not simply “going through a phase.”
I think that you need to be brave, stand up to your fear and tell your parents about how you’re feeling. An easy way to do this would be to show them the letter that you wrote and my response. Your letter probably says everything it needs to say about how you’ve been feeling.
To answer your questions directly I do not think that you’re overreacting. Secondly, I absolutely do not believe that you should continue to withhold this from your parents. As I mentioned earlier, depression is very treatable but it requires that you are open about how you’re feeling so you can begin treatment. The last thing you want to it to keep this a secret. By keeping this to yourself, you risk allowing the depression to become worse. I hope that you will consider telling your parents the truth. Thank you and let me know how you’re doing in the future.