Hi all

I actually didn't know how to name this topic,so....
Well, I sang in a choir for 4 years and I always had problem with standing in tune, I have good voice, can sing high, but standing in tune is really kinda hard for me, not that hard when singing alone though.
But, the problem is with me singing the modern songs....I can learn melody almost with no problem and sing it well, but when I try to sing it with music I sometimes forget melody or just start to sing instrumental melody....Even if I sing correct somehow my voice is quieter and doesn't have that range like when singing without music...
Hope I have described it well and hope that someone can tell me why that happens to me
tnx