This one is brutally honest. La Adictiva sing from the point of view of someone in a secret affair who never promised anything: "Nunca se habló de algo formal" (nothing formal was ever discussed) and "era sexo y nada más" (it was sex and nothing more). When the other person starts catching feelings, he shrugs: "¿Qué te pasó? Te confundiste" (what happened to you? You got confused).
The chorus is where it stings. He enjoys what happens "en esta habitación" (in this room), but warns "no te hago el amor" (I'm not making love to you). He has to leave and answer "si ella me llama" (if she calls me), so there is someone else at home. The best line for learners is the last one: "No te ilusiones con lo que nunca será" (don't get your hopes up about what will never be). Ilusionarse is a great verb that English has no single word for: it means getting your hopes up. And that shout of "Adictiva" in the middle is just the band calling out its own name.