I can't imagine any boundary issue with giving him creepy drawings, since they are for the purpose of describing to him what it feels like to be inside your head. You could describe these attacks in words, or you could draw them, but either way you're communicating what sounds like suffering that you are going through. Your T would want to know about that suffering, and the nature of it.

Our T's hear about a lot of frightening and painful experiences, but that's the nature of their jobs... I think it's absolutely okay to show him the drawings.