Translation - Turkish-Spanish - keşke bana inansaydın,her zaman ruhumda kalacaksın

I looked up how to say "if only" (I was translating from the not-yet validated English version as I don't know Turkish) and it said "aunque sea sólo." I applied it into my translation and it didn't sound quite right so I just used "si" (meaning "if") instead.

My translation basically says:

"If you had believed in me, you will always remain in my heart."