CC-
Is ML your screen nickname?
After reading your question and Elden's post, it appeared to me that the ages had gotten switched.
I personally think that the two of you are probably too young to think of marriage, but you have taken the relationship to the point that is equivalent to ripping a feather pillow open in a hurricane. There is no way to go back to where you start, so you will need to make the best of this.
I would strongly urge you to become actively engaged in marriage counseling and possibly some type of partner therapy (possibly as a group). I do not think that you are nuts. I am urging the two of you to get as many bullets out the the chamber as you can before you pull the trigger.
No kids until both of you are out of school and employeed.
"his grandparents are all for it." I will bet you dollars to donuts that this position is based on extreme selfishness--------------- They want to have a great-grandchild.
I wish you the very best. I hope that you will be able take several of your children to visit Elden in the nursing home in 20 years.
Shalom,
Jay