Being gay isn't a sin. For some people it's simply the way things are.
Yes, it is a sin.
For this reason God gave them up to vile passions. For even their women exchanged the natural use for what is against nature.Likewise also the men, leaving the natural use of the woman, burned in their lust for one another, men with men committing what is shameful, and receiving in themselves the penalty of their error which was due.And even as they did not like to retain God in their knowledge, God gave them over to a debased mind, to do those things which are not fitting;being filled with all unrighteousness, sexual immorality, wickedness, covetousness, maliciousness; full of envy, murder, strife, deceit, evil-mindedness; they are whisperers,backbiters, haters of God, violent, proud, boasters, inventors of evil things, disobedient to parents,undiscerning, untrustworthy, unloving, unforgiving, unmerciful;who, knowing the righteous judgment of God, that those who practice such things are deserving of death, not only do the same but also approve of those who practice them. - Romans 1:26-32
http://www.biblegateway.com/passage/?search=Romans1:26-32&version=NKJV