We may have difficultly understanding our faith. However, it has been said that ten thousand difficulties do not make one doubt. To doubt means to be unsure whether a belief is true; to have a difficulty means to know the belief is true but to be unsure just what it means or why it is true. This can be overcome through prayer and study. If Jesus tells us something is true - then it is. Same goes for His Church. 

As Catholics, we shouldn't allow difficulties in understanding Church doctrine to turn into doubts about established truths. The Church has spent its entire life carefully examining ideas and determining which ones are in line with God's law and which aren't. It has discarded heresy after heresy while carefully building up the tenets of the Faith. 

There are thousands of other Christian churches in existence today - all of them had "doubts" that led to "new ideas" which at one point the Church had decided were outside the deposit of faith.