Knowing things that I'm not supposed to know

Recently, I've found myself in situations where I know things that I'm not supposed to know socially. For example:

• Learning about a serious medical diagnosis.
• Finding out someone's sexual orientation.
• Hearing that two people have broken up, but they haven't shared the news publicly.
• Being told that someone is having financial trouble.

While I'm flattered that people trust me enough to share what's going on, it's uncomfortable being unsure about what people know that I know.

Should I tell people that I'm there to support them even if they haven't shared their news with me yet? Or do I just wait for them to have their own conversation with me? To err on the side of safety, I've opted to wait, but I wonder whether it would be easier for my friends if I just told them that I know.