Well, yes, it was. Everyday life was nearly connected to religion, to the church. If you are interested in history you probably know a bit about Czech reformist Jan Hus, about Hussite wars, Czech brothers and so on. But anyway, short overview can make it a bit clearer.
It took quite a long time before all Czech people became Christians. First Czech duke was baptized in the 9th century, but it took about 3 centuries to spread the word of God all around Bohemia, Moravia and Silesia. The people were Christians - catholics.
But as the time went there were quite many wrongs steps taken by the priests, quite many wrong things done by them. Jan Hus started to criticise the manners of the church and he was burnt to death in 1415 for his opinion (this is really shortened, if you want to know more, see Wikipedia). The Hussite movements raised in the following years and the Hussite wars began. The utraquist religion was founded during these years and many people living in Bohemia became member of utraquist church.
Another church, Unitas Fratrum (Jednota bratrská), was founded in the middle of 15th century. As these two churches were Czech churches, they were much closer to the common people than catholicism. It is said that about two thirds of people were members of these churches before the 30 years war.
The Hapsburg dynasty became Czech kings in 1526. This dynasty was catholic and wasn't too happy about reigning the quite non-catholic country. But the conditions were set and the king respected it less or more until the first half of 17th century. But... 1618 the Czech noble men started an uprising against the king, elected another king (who was protestant) and the 30 years war started. Czech uprising was defeated in 1620 and the recatolization began.
Ther was only one possible religion - catholic. Who wanted to stay protestant, was forced to move out of the Czech lands - but this was only valid for noble people. The common people were under huge pressure to accept catholicism as their only religion, so they publicly did so. But in private quite many of them were still protestants.
People were allowed to join other religion than catholic after issue of the Edict of Tolerance in 1781. They could choose from three other religions - Augsburg (Lutheran), Helvetian (Calvinism) and Greek orthodox. Most of people who changed the church decided for the Helvetian religion which was closer to the original Czech churches which were not allowed.
After the end of Austrian empire people were allowed to become churchless. There also rised a number of new churches which were forbidden before - new Czech Brothers, Czechoslovak Hussite Church and so on.