What are the benefits to proposing right now? You have a great thing going, can you just enjoy it for a year or two? I don't know what the rush would be or if there is a reason that you want to be married so soon.
My advice would be to wait for a couple of years.
Right now your brain is being swamped with all of the neurochemicals that come from a new relationship. It is great. You should enjoy every minute of it. But there is no need to rush into marriage, which everyone wants to be life long, when you are under the influence of these powerful brain chemicals.
Wait a couple of years for your relationship to mature. Then you can be more confident of the foundation of a long term relationship before making this long term commitment.
Enjoy a great exciting relationship for now, savor every moment of it.