I started dating my now husband when I was 18 (now 26) we got engaged after 5 years and married after 6. Had we gotten married years 1-3 I am almost certain I would currently be a divorcee in my 20s. If you can help it please wait to propose. She may be the one but marriage isn't casual, it's a massive commitment and you need to be certain that it's the right move. If you do propose, stay engaged for a long while. I know my stranger on the internet advice means nothing really but take it as youd like.