Being in the closet is a very dark and depressing experience. I firmly believe that God wants us to live honestly and authentically.
Since you are only 19, you are probably still to an extent under your parents' authority. I think it is very valuable to be open and honest with people. especially one's family. That might be tough in your situation, but I would definitely head in that direction if I were you. Make sure you are independent enough and strong enough to endure the difficulties that might follow.
And being gay is definitely NOT a sin. We cannot let people convince us of that. The Bible does not support such an idea; it is all man-made interpretation. Being gay is the way that God made us, and he/she knows what is the best.
And don't let yourself get into suicidal depression. There are always people to ask for help and there are so many of us who have been through similar experiences.
Tu amigo, Pablo
For I am convinced that neither life nor death...neither the present nor the future nor anything in all creation will be able to separate us from the love of God that is in Christ Jesus our Lord. Romans 8:38-39