<human>: Could you distill the essence of the text into 1-3 sentences?

I've been with her for about 5 years, she's only the second girlfriend I've had, and we agreed from the start that 5 years was our threshold to marry. She as all of the qualities of a great wife and potential mother of children, but I'm uncertain if I want to marry her, or even marry in general. Is that in itself a deal breaker? Pretty much all of my married friends had no doubt that their wife was *the one*, but I've never felt that way.     

I'm honestly not sure if I'm *in love* with her as much as I just love her, I don't feel much lust towards her like I did in the first couple years, but I love her companionship and her company. I've been thinking about breaking up lately due to this uncertainty and that I'm possibly just wasting her time by stalling on this decision. I think this is putting pressure on the relationship, we argue and disagree a lot lately as I become less invested in the relationship I am much more outspoken and opinionated on issues, where I would previously keep my mouth shut just to keep the peace. We definitely have communication issues, which probably stems from a lack of relationship experience with other people.     

Should I let her go? She's absolutely keen on marrying me, but I'm just not ready, and I don't want to waste her time. The thought of breaking her heart kills me, but deep down it feels like a necessary evil. If I did break up, what's the actual process of doing so? I rent a house with her, we have shared furniture, a pet, etc. I imagine it would be a really difficult process for both of us.
<bot>: Girlfriend of 5 years wants to marry, I'm not ready, and not sure if she's "the one". Our relationship overall is good, but not amazing. Should I move on, or try to make it work?