Hello Charly, You could say: " I am not sure, I could (should) tell you my secret."

"I'm not sure if I should tell you my secret" sounds better

Hi... That's ok...

Yes, it's ok. I got the idea. You want me to shut my mouth after you tell me something really important for you, and the fact you trust on me to keep it.

To say this formally it would be, `I am not sure I can confide in you.` or casually `` I am not sure I can trust you with this secret`` or ``Would you be able to keep my secret? ``