First, I'd want to make sure you guys had watched "Why men don't want to get married" https://www.youtube.com/watch?v=1t6j50Tkwy0 and "Why men don't want to have kids" https://www.youtube.com/watch?v=dujXV7D7RXo
I think that may help narrow things down a bit. I was pressured into marrying my high school sweetheart at the age of 24. I was going through the motions because it was what everyone expected of me. We dated for 8 years before marrying. We had kids. I divorced recently, after 17 years, and now, with taxes, child support, and alimony, I get to keep about 20% of my income. Its horror stories like mine that strike marriage fear into the hearts of every young productive man, and frankly, they SHOULD. Fortunately for me, I managed to find the love of an amazing woman that I do intend on marrying. However, the ONLY reason we are marrying is because without doing so, there are people with guns that will prevent her from staying on this side of an imaginary line on the ground for an extended period of time, or permit her to make a living. We do not seek to have the State or Church condone or control our relationship by licensing and certifying it as valid. That is up to us. That being said, we DO NOT live in a Stateless Society, unfortunately. So, in order to be productive, we DO have to play the game at times, and there ARE advantages to getting married in this Statist Society .... taxes, healthcare issues, and affairs of estate come to mind.
Your fear of marriage is well founded ... just look at my condition ... and consider Stefan's take on it. However, it IS a significant gesture regarding your willingness and commitment to the relationship. I can't blame women for wanting that level of commitment before having kids ... being a single mother without help or financial support is tough. Encumbering the man in the relationship with the threat of violent coercion should he decide to call it quits later down the road seems an attractive option.
I suggest you both be honest with your fears and consider the pros and cons. Just don't EVER do something just because you felt that is what was expected of you by society, friends, family, whatever.