Dear Jennifer, 

You have asked a fundamental question, and I will try to be as clear as possible with my answer - and you may be surprised by it. 

Jennifer, respectfully, there is some confusion in your thought pattern. A Catholic is someone who has been given the gift of faith, and takes care of that gift by being docile to the Holy Spirit, striving to understand its content through prayer, reading and study, but always under the guidance of the Holy Spirit, who leads the Church and gives it the charism of fidelity in matters of faith and morals. What I mean is, we as individuals - individual writers, theologians, priests and laypeople - can make mistakes, the Church never will in its official, defined teachings. So when we have a truth such as Mary's sinlessness, the infallibility of the Pope, etc... that the Church teaches expressly, we are not really Catholics if we reject it. 

If we do not understand it and have questions, that is another matter. In that case we should inquire and study so as to find the answer. I have often found in discussion that people who reject certain teachings (dogmas) of the Church either do not understand them as the Church does (for example thinking that infallibility means that the Pope never makes a mistake, or that Mary's sinlessness puts her equal to or above Christ) or have not been given access to the reasons the Church teaches them, or do not understand what we mean by Tradition, etc... There can be many reasons, often with no blame to the person. 

But once you realize there is something up, you have to start doing something about it. It is usually the beginning of a wonderful intellectual and spiritual adventure, because the truth has a beauty and attraction all of its own, and it has real consequences in our lives, it can change them. 

I would recommend you get a copy of the Catechism of the Catholic Church, and begin your study by looking up those areas you think you have a disagreement with. The Catechism has very helpful indexes, and is very well written, it will give you a lot to think and pray about. 

Also, look up websites that deal in Catholic apologetics, you will find many of the points you have a problem with discussed there, Catholic Answers is one of them. 

Very importantly, pray. Ask Jesus to show himself to you, ask the Holy Spirit to guide you. I am sure you are seeking the truth, but the truth is not always the most comfortable, and sometimes we have to contend with some lingering intellectual pride no one likes to be told they are wrong.  

And no, I would not recommend that you pursue a vocation until you have these issues resolved. 

God bless, let me know if I can help you further, and be sure of my prayers.