When you know...

So I keep reading comments about relationships with... When you know you know... I'm trying to understand because I've never felt this way about anyone? Well...I kinda did with my now fiance but when we moved in and he dragged his feet to propose I lost a lot of it...I also realized I can't adapt to him very well. We've been together for 6 years now and I've yet to feel the way I did... A lot of times I wonder if we'll stay together. I'm posting anonymously because I'm a little ashamed of these feelings. We have a 2 year old and I have a 9 year old from a previous relationship... I'm afraid to start over and that perhaps I need to focus on the positives. Any feedback is greatly appreciated