It's my understanding that they see us and hear us, whether we speak to them out loud or in our minds. If you feel paranoid that he's reading your mind, it's OK to set boundaries. Tell him not now or ask him to visit you in a dream, or in some other way. Some people feel scared about opening themselves up to negative spirits, so it's good to have an affirmation, like saying, "Nothing negative/evil has permission to be near me," etc. I flat out tell negative spirits to fuck off, but that's just me, lol.