I believe if you have been together this long that medical school is not going to cause you to get divorced. You will be fine. When my husband went to medical school, he was both married and had a 3-year-old son!!!
My recommendation is to get married and to find a babysitter that you can rely upon in order that you can go out on a date. If you can go out once a week or every two weeks that would be good & healthy. Sometimes that won't work out, but it is achieveable!!
There is no good or bad time to get married and/or have children. You have just got to adjust your expectations and bend a little. It was personally shown me and taught me to become even more independent and guide my own life. It's an adjustment, but because I chose my husband as my life partner, I am willing to sacrifice. I have found that our marriage helps balance his hectic life in medical school and residency. He has consistency in his life. He doesn't have to worry about going home to an empty house and he has something to look forward to when he walks through the door... HIS CHILDREN!!! They just adore him and love him no matter what!!! That's a great feeling & something to really look forward to after a day of hard work & thinking of diagnoses & follow-ups $ medications all day, not to mention those relationships with other colleagues & attendings.
So, do not fear getting married before medical school. Embrace this new chapter in your lives and know each day is what you decide to make of it!! This is a more challenging part of our marriage, but we look back from where we came and think "we" did it with big smiles on our faces!!! There is nothing to us more precious than our family! I hope I have helped!
C~ya!
Christy