My cousin posted this today on her FB page. Twenty-five years ago, a week before my cousin was to get married, she started wondering if she was making a mistake. She had to get alone with God and pray to really seek answers and to beg God to help keep her from making a mistake. In the end, she realized she had cold feet. And their marriage has been extremely strong.
I think, what you need to do is to get with God, by yourself, and pray. Read the scriptures and just wait for God to answer you. Do not make any decision until you hear from God.
While your waiting for God to answer, look on your past and see if someone in the past has hurt you in such away that it makes it hard for you to be in a commitment. If the answer is yes, then ask yourself why. Have you forgiven the other person, have you sought God to heal your heart? If the answer is no, then you need to ask yourself if you've been single for so long, that the idea of being married scares you. If the answer is yes, explore that, if no, then continue searching your heart. Eventually you will find the reason you do not wish to be married. You may find out that you are scared, or you may find out that God does not wish for you to marry at this time, or not at all. No matter the reason, you will only find this out if you seek God.
We can all tell you what to do, but the fact is, we don't know the whole situation, only what you tell us. We don't know you in person, we don't your boyfriend, and what he sees. And to be honest with you, if I were engaged for about a year, I probably would be pressing for a date. And if someone told me they were not wanting to be married, I would be pretty mad, especially if they didn't tell me why.