First of all 14 months is only slightly more than a year of dating!
Sometimes it takes people a good 2 years to really get to know a person. A lot of times people make the mistake of making a "commitment" during the "infactuation phase" of a relationship.
They don't know how the other person handles stress or disappointments in life (especially those coming from their mate)
You have to go through a little adversity with someone in order get the full picture of what you're dealing with.
Dating for 2 years is about long enough to find out if this is a person you want to spend the rest of your life with.
After 2 years maybe you get engaged, set a date for 1 year out and spend that year living together. This will give you an idea as to how household chores would be handled as well as sexual compatability. Does the frequency and quality drop significantly?
You want to do all you can to make sure you're making the right choice. Jumping into a marriage and then trying to "fix it" after the fact is big mistake. The real "work" is in selecting (the right mate). Once you've done that the so called "work" in a marriage is more akin to a "Labor of love".
You need to ask yourself "Why is getting married so important to me?" Do you want to marry HIM because he's "Mr. Right" and you're "Madly In Love with him" or is it because you're 36 and just want to get married? What is the upside for him?
Is it a security issue? I'm sure you are aware the divorce rate is near 55%, Saying "I do" does not mean "forever".
With regard to a "Trial Separation" it's really a "practice breakup" without the drama of a messy break up.
You'll see each other less and less, talk to each other less until one day they say, "I think it would be best for us to move on with our lives". By now the "shock" of breaking up is gone and usually it's a forgone conclusion before "the talk" even happens. I once wrote a blog about this.
The next step for most people is seeking "Closure".
Personally I think it's overrated. Ultimately the goal in life is to find someone who loves and adores you for who you are! In case you want to read my take on closure see below.
Best of Luck!