You have not given any example of misunderstanding. I just wanted to know whether your are arguing on serious things or silly things. Anyway it is your personal matter.
What I understood:
You both have not good understanding between each other due to which your start arguing and then fight with each other.
Your boy friend understand you more then you. Because he most of the time forget your mistakes.
You both have feelings and love for each other.
First of all you should rethink about your past misunderstandings. Can you avoid that? Do you have another alternative to solve those misunderstanding rather then arguing.
Be positive with your life. When two people become life partner then many new things come to their life. If you are able to manage all the things till now then definitely you will able to live happy married.
Love and marriage are based on trust and caring. Remember each other caring and loving time. This will help you to release your tension.
If you are planning to leave this person then what will assure you that future man will understand you and care you?
Ans yes you are not mad These things are normal. So enjoy your life!!