I am Catholic, but I disagree with so many church teachings!?

I'm 16, and raised Catholic. I will certainly always love my Lord and savior Jesus Christ, but some parts of the church I disagree with. Sime rules, it seems, are just made up by the Catholic Church. For example, mortal and venial sin are never mentioned in the Bible, and many teachings, it seems, were made up to help the church gain power. (Apparently this has been seen throughout history, just ask Martin Luther.) As a youth, I never had Bible study, just Catechism study and... I just need some advice... Where do I go from here? Should I try to find a Protestant youth group perhaps? I am finally able to think for myself and yet the answers are so hard to find.