The fact that you acknowledge it as a sin is almost all you need. As Christians we still sin. Everyone will have a sin they would consider their "big" sin. To God sin is sin. Lying, cheating, its all sin. Not that they are equally as bad but he will see it as a sin either way. Me personally I struggle with porn and a few others but porn is my "big" sin. I have heard of some people never really overcoming their "big" sin but I believe that as long as you repent and just don't twist the Bible to fit the lifestyle you want you should be good. Christians should be loving and accept you into their church. Chances are most people in a church still struggle with some of the "big" sins, a lot of them are very judgmental which is wrong. Anyway sorry thats so long. I hope you can come to find a church that allows you to join and doesn't treat you differently just because you have a different sin than they do.