Ranting ?

Secrets

So... I have a secret. It's personal, and I don't want to share it with anyone. I have a best friend (more of a brother) that I told I have a secret. I never told him the actual secret, therefore, he bothers me everyday about it. He never shuts up and asks me about it constantly. I want to tell him I really do, but I can't. It's on such a personal level that I can't even fathom the idea of telling him. He keeps saying "I told you my secret" which is true. He told me he was gay. I kinda already knew that because I can just tell, but mine is was worse. I didn't want to quite say what it is, but it involves depression and worse. So this is my "ranting" page where I can get out my feelings... I need help. I want to tell him cause he is my best friend. I'm just afraid that he'll tell people. It's such a serious thing and he isn't a serious person. I swear he acts like he is 2 years old. Anyways, I don't know whether I should tell him or not. I'm confused and stuck. I have tried to tell him, but I have backed down every time. I just can't do it!!! What should I do??? HALP ME!!!!!!