Everything that your heart says is wrong, its wrong. Like you said your religion say you to "If one doesn't go to the Church on every Sunday, he is a sinner". its wrong because your heart did not believe on it. Because NO one religion bound you to pray. There are out comes if you dont pray, but not the boundness.
I agree with this but probably 99% of Catholics believe in this as it's written in the Bible. One person who lives in my neighborhood goes to Church twice a day and then he himself beats up dogs for sitting on the streets. Isn't this a sin to beat innocent people? That's the reason I don't believe in this and I don't go to Church every Sunday. Let them say that I have committed millions of sins till date and I will go to hell. I proudly will accept that.
Don't forget that they've made a contradictive statement about that for centuries, they say God is everywhere, so why the fuck do they need a Church?
People believe that God is only present in Churches, Temples, Mosques, Fire Temples and so on when God is in our heart. I can say my prayers even at home but that's not called a prayer according to the priests.