"Cómo Expresar Lo Que Siento" (How to Express What I Feel) is a vallenato about a man who simply has too much love to hold in. He opens with "En mi pecho ya no cabe tanto amor" (there's no more room in my chest for so much love), a love "atrapado sin salir" (trapped with no way out). He doesn't know whether to stay or go, and he asks his corazón (sweetheart, literally "heart") to decide for him.
The chorus is the whole dilemma in one line: "Te amo y no dejo de pensar si callar o decir lo que yo llevo dentro" (I love you and I can't stop wondering whether to keep quiet or say what I carry inside). He admits it hit him out of nowhere, "de repente" (suddenly), like "una loca pasión que se adueña de mi mente" (a crazy passion that takes over my mind). Halfway through, the singer drops in classic vallenato saludos, spoken shout-outs: "Este es el sentimiento de Israel David" and a dedication "con cariño" (with affection). The ending just repeats "tu corazón" (your heart) over and over, which is a bit much, but that's where he wants to live.
Grammar tip: te amo and te quiero both mean "I love you", and this song uses both. No puedo evitarlo (I can't help it) is a phrase worth stealing.