<human>: Condense the text into a few key points

I have been with my boyfriend for the past seven years, living together for the past 2. We have made it clear to one another that we want to be together forever and see us getting married one day.
However, lately, the more I try to talk to him about it, the more reluctant he is to talk about it. It often leads to arguments but I don't know how to discuss it with him without him getting defensive. I'm worried I'm starting to nag as I feel the need to talk to him about it but he just gets defensive or walks away without anything being resolved. 
He has told me that the only thing stopping him from proposing is that he does not have the money for a ring, but I also know that despite his well paying job, he has made no effort to save for one and I'm starting to feel he is using this as a convenient excuse.  Iv made it very clear that he does not have to spend much on a ring but he doesn't seem to believe me. He admits he doesn't see how getting engaged "will change anything". He is also under the impression that once we are engaged he will be expected to pull $20,000 out of his ass to pay for a wedding (which is not true).
I don't doubt that he loves me and wants to be with me but he is the type of guy that avoids making big decisions until he is forced to make them by being backed into a corner (he didn't want to think about applying for jobs after college until 4 months after he graduated). If he is not 100% on board with something he will drag his heels. I don't want to nag him but I'm starting to get hurt that after 7 years, and with him knowing that this is something important to me, getting engaged is not a priority for him (any time soon it appears)
Any advice would be greatly appreciated
<bot>: been together 7 years, bf says he can't propose because he has no money for a ring, but making no effort to save for one.