Much the same happened to me, Darius. I'd left home by the time I was 19. My parents were church going conservatives. I'd already stopped going to church for the most part before I graduated from high school. I just hated going. Later my politics changed. I became an agnostic nonpolitical person.
Regarding religion, it's best if you just keep it to yourself until you one day leave home. It isn't worth the hassle of trying to explain what you can no longer accept. It might be seen by some a blasphemous. At 19 religion is not likely the hill you want to die on. Sometimes it's just better to let it ride and be silent.
Politics often equals religion these days. Not everyone feels that way, but more do so than I have ever seen it in my lifetime. If you can ignore the religious parts of political discussions then speak up. Just remember that often the people you may disagree with cannot or will not separate their religion from their politics. You likely won't win those debates/arguments.
In time your feelings about religion and politics will likely change and change again.
I never returned to Christianity and many in my family have become less committed to it over the years, though some have become religious fanatics. We all share mutual respect. We avoid talking about religion save for 2 cousins who can't seem to wait to tell me about Jesus or ask my about my soul. I avoid them.

Most of the family does. We all talk a little about politics and while we don't always agree most of my family and extended family has all but given up on the two ruling political parties. I am a registered Independent. My family and extended family are disgusted with Washington and that includes Congress. One of my brothers has never registered to vote. He use to get a bit of hell about that, but these days we're thinking he may have just been smarter than the rest of us.
Point is, except for a few my family members have evolved over the years and we are closer politically and probably religiously. We are more accepting.
It is important to be who YOU are. At 19, you should be deciding for yourself. It is healthy that you are. It is good to question. Truth prevails. Nothing is going to happen overnight. Be patient. Chances are you're going to come through it just fine.
Give your family time, especially if you are living under the same roof.