Te veia sufrir todos los dias y yo sin poder hacer nada al respecto.
I would see you suffering everyday, while I was not able to do anything about it. (You could also say "saw" but the prosody of this particular sentence is not as literal as it seems).
Tenia que buscar la forma de desirte que estabas en peligro.Te veia llorar y lo que mas me provocaba era abrazarte y decirte cuanto te amo.
I had to find a way to tell you that you were in danger. I would see you cry (*Again, you can also use "I saw", but there is more depth to this expression*) and it would provoke/make me want to hug you and to tell you how much I love you. * I corrected some of your Spanish spelling there :)
Decidi buscar la forma de que tu supieras que yo estaba ahí, y fue Ode Mae quien me ayudo, atraves de su cuerpo, a poder sentir tu piel, a olerte y a volver a revivir esos hermosos momentos que pasamos juntos.
I decided to find a way for you to know that I was there. I went to Ode Mae, who helped me, through her body, to feel your skin, to smell you, and to relive again those beautiful moments that we spent together.
Tu seguias dudosa pero yo te dije que you was wearing the shirt that I spell margarita on, and the earings that I give you for Christmas, and you finally realize that I was there…..
You were still doubtful, but I told you that you were wearing the shirt that I spilled Margarita on, and the earrings that I gave you for Christmas. And you finally realized that I was there.
*Pay attention to your spelling in English as well*
As a final touch, I would add a significant phrase to this letter, which is true to this particular work. Add how the ghost feels about being able to come back to life through Ode Mae's body. You may want to add at the end: "It was great to feel alive again" or something to that effect.