Hello, I am Rafael. Thanks for asking your question - I'm here to support you. (Information posted here is not private or confidential but public).
I am sorry to know about this challenging situatiton you have been facing, but feel glad to know you have developed this strong friendship.
It seems from your story that you have been sharing for a while and truly enjoying each other's company,and that for the past two years it has got even better, and that's why you feel this way and long for it to evolve into a new phase.
You clearly describe how both of you do not like/want the other to date other people, but at the same time have totally avoided discussing anything about what you truly feel for each other, than while in the past you were clear you were just friends and did not want anything romantic, your friendship has evolved and your own behaviors show how this has changed. Your words clearly show that, even when denial and avoidance have been the strategies you have used all this time not to talk about it, while getting closer to each other.
I sincerely believe that one of you need to take the initiative and start talking about it, that your friendship/relationship needs to start being more open and honest for it to evolve and grow healthier and to become more fulfilling too. of course it is not easy since you have literally built it avoiding being like that, but as you can see, without working on maturing it, you would feel increasingly frustrated, conflicted and confused, which would undermine instead fo help what you already have taken care of for this long.
Does it make sense?
I'd suggest you to read this book: "Single Men Are Like Waffles - Single Women Are Like Spaghetti: Friendship, Romance, and Relationships That Work": http://www.amazon.com/Single-Men-Like-Waffles-Relationships/dp/0736922490/ref=sr_1_9?s=books&ie=UTF8&qid=1388749934&sr=1-9&keywords=friendship+romance It's a very practical and easy to read guide about relationships for single people.
"The Five Love Languages Singles Edition": http://www.amazon.com/Five-Love-Languages-Singles-Edition/dp/1881273873/ref=pd_sim_b_3 and this one will help you with your friendship and every relationship in your life.
Please feel free to contact me if you have any further questions and to follow up, since I am here willing to support you as possible. Thank you for your trust. Take gentle care.