What does it mean if a boy only treats you as scum? When I am with you, I will dump you immediately after chasing others, live together and travel openly.

A boy only cares about you, which means he doesn't care about you. If he cares, he is afraid of falling into his hand and melting into his mouth. Being eaten by others now means that he cares about that person, so he will be eaten. So the reality is cruel, and fantasy is unnecessary.