I voted that you should stop thinking about it, when it happens it happens. I know that when Brett and I graduated college I really wanted to get married - but it didn't happen. Now, 7 years later it's happening and it's the perfect time.
You need to not stress so much about when it happens. I know, easy to say when you have the bling, but it's true. All this time you are stressing about when it will happen is time you aren't focusing on the actual relationship and how great it is. Just step back, say "I have an amazing man who loves me and isn't going anywhere", and let go. Once you do that, the proposal will come.
My second choice is get married without the ring. Rings are great and shiny, but they don't mean anything with respect to the vows and the promises you make. It's just a symbol - nothing more.