He doesn't know about the way you feel about Him.
He will never know probably.
And He will definitely never feel the same way.
You don't remember when you fell in love with Him. It was long before you literally fell. You know that because every time you had your grace ripped away and you slammed physically into the cold hard earth you saw His face, smiling, laughing; alive. And you knew that you were doing it for Him and that made it ok.
No, you can't remember a time when you weren't in love with Him. There must have been a point when you realised but now all memories of Him are tinged with that empty, aching longing for Him. You can remember watching Him rake leaves after Sam had been trapped in the cage, wanting to reach out and touch him; to comfort him. But she got there first. Lisa was beautiful and feminine and most importantly she made Him happy, which is more than you could ever do.
It seems funny to you now, looking back on a time when God was the only Him, with a capital H. But God is long gone and He took his place as the most wonderful thing in creation. Of course, He doesn't realise that and the amount He hates Himself makes you want to scream in anger at the unfairness and pain of the human world. Why can't it see how wonderful and kind and selfless He is? Can't the world see how funny, clever and sweet He can be? Death sort of saw it, so did some of the angels but no one except you seems to be able to see how perfectly imperfect He is.
You pulled Him out of hell, kicking and yelling the whole way in that stubborn angry voice that you could have never guessed would become so important to you. You saved him that first time and you kept saving him because you had to, out of duty and then out of, well, love. He wasn't always grateful but the times you had with Him made it worth all the sacrifices.
And you both messed up. You betrayed Him - not wanting to but you did. And you messed up. You lost His trust, one of the most important- one of the only things you had. The Levaithans ripping into your soul had been painful but no where near as painful as seeing the disappointment and betrayal in his eyes when he realised you were working with Crowley. And since then you know it will never be the same- He won't trust you the same way you trust Him. Especially since Metatron.
And, okay He's betrayed you too. He sent you away from the bunker when you needed help most. That had been painful. But you know He will always but Sam in front of you and you're alright with that.
You're alright with just being His friend. As long as He is alive and happy you would be alright not seeing Him ever again, even if you had to live for a thousand years more. You would die for the Righteous Man without question - you have died for Him.
There is nothing you wouldn't give up for Dean Winchester.
