[Mrmerlin]

Joe I think you need to figure out what YOU want , if its just her on top sex, then having children with her or anyone for that matter isnt something your interested in.
OTOH if you want to start a family make a child, if you like her more after that marry her.
Before you do anything you must BOTH be on the same page and discuss the responsibilities of this decision.
If you have any red flags for you then you might have your answer.

Sex is good at night and in the morning, after that being able to walk away is definitely less of a responsibility