Desvelándome comes from the reflexive verb desvelarse, which means "to stay awake all night" or "to lose sleep". It's a very evocative word that goes beyond simply being awake.
In the song, Jay Wheeler sings, "Sigo desvelándome, pensando en nosotros" (I'm still staying up all night, thinking about us). He uses this word to express the pain of sleepless nights spent obsessing over a lost love, perfectly capturing the feeling of lovesick insomnia.
Ever wake up from a dream so vivid that reality immediately ruins your morning? That is the exact mess Puerto Rican singer Jay Wheeler walks us through in "Te Soñé." The beat belongs to reggaeton, but the mood is completely stuck in the past. He admits right off the bat, "Anoche soñé contigo / Soñé que estabas a mi lado como antes" ("Last night I dreamed of you / I dreamed you were by my side like before"). He even knows his ex is already with someone else ("sé que tienes a otro" [I know you have someone else]), yet he keeps losing sleep over old memories stored in his phone and his head: "Tengo recuerdos en mi historial" ("I have memories in my search history").
His daily routine without her sounds pretty miserable, honestly. He sings that he relies on pills just to shut his eyes ("Para dormir, necesito pastillas" [To sleep, I need pills]) and spends his hours drinking while waiting by the door: "Te sigo esperando / Sentado en la misma silla" ("I keep waiting for you / Sitting in the same chair"). The Spanish here is direct and conversational. When he confesses, "Contigo me tropecé / Dolió cuando desperté" ("I bumped into you / It hurt when I woke up"), he treats running into her inside his subconscious like an accidental crash. It is an unvarnished confession about wishing you could fall right back asleep just to hold onto someone who is already gone.