De otra forma no se puede comprender,
It can't be understood otherwise
de ti estoy profundamente enamorado,
I am deeply (profoundly) in love with you.
necesario ya era hacertelo saber,
it was necessary to let you know already
hacerte ver, que yo te amo.
To make you see, that I love you.
Que en mis sueños tu no dejas de existir,
That in my dreams you don't cease to exist.
que me tienes totalmente cautivado,
That you have me totally captivated.
con tu forma de mirar, de sonreir,
with your way of looking, of smiling
la voluntad sencillamente me has robado.
you simply have stolen/taken away my will
Necesito decirtelo, que tu sepas que te amo,
I need to tell you it, (so) that you know I love you.
es preciso que entiendas que te estoy necesitando,
It's necessary that you understand that I'm needing you.
que ya nada me importa, solo estar a tu lado,
That nothing matters to me, only to be by your side.
que mi vida ya es tuya y tu ni cuenta te habias dado.
That my life is already/now yours and... you hadn't even realised it
Dimelo con tus ojos, que es mas que suficiente,
Tell me it with your eyes, that's more than enough
que para ti ya no te soy indiferente.
That for you, I'm not unimportant/irrelevant any longer
Nice job!! 

“If cats looked like frogs we'd realize what nasty, cruel little bastards they are. Style. That's what people remember.” ― Terry Pratchett.