Not for being poor or ugly, but for longing
I have the black shirt
Or: I wear the black shirt. Black is likely a reference to funerals, where people wear black
Today my love is mourning
Estar de luto = to be visibly mourning (a death)
Today I have in my soul a sorrow
And it's because of your spell
Or: And it's the fault of your curse
Today I know that you don't love me anymore
And that's what hurts me most
That I have the black shirt
And a sorrow that hurts me