What is my boyfriend's mentality of adding me with a trumpet?
First of all, he added you with a trumpet, probably to test you. He may not be sure whether you have that kind of unswerving feeling for him, and he wants to test you as someone else to achieve his sense of security. If you think he is a good man, you can tell him directly and reassure him. If you are not sure or feel dissatisfied, you should be prepared for the future.