I'm not sure it's really even possible to enjoy being close friends with someone, when deep down you really wish it could be more than that. I think you may be putting yourself in an impossible situation by spending a lot of time alone with him. I think that what you are asking of yourself is beyond what humans are capable of. It's nice that you two care for each other and value the bond you have. I'm not suggesting you just throw that away. I am suggesting that you detach more from him. The only way I know of doing that would be for you to not be alone with him very often.

You are keeping up a level of emotional interaction with him that really does not fit with who you are to each other. This is just asking to stay in constant emotional turmoil. What you are doing to yourself isn't fair to you. He, apparently, doesn't realize the pain you are experiencing. It might be best to let him know that you are there for him, but that you have to move on toward finding the love that you crave. You won't really give any other man an honest chance, while you are nursing this devotion to someone who you see as unattainable. Also, you'll resent his finding someone special, which isn't fair, if you accept that it's not going to be you. You need to let go and stop torturing yourself. You need to put some distance between you. If he is caring friend, he will understand. Being "extremely close" with him is really not appropriate. It's not healthy, and you won't be able to make it work, as you are trying to do.

I'm sorry for the pain you feel. It's not because you are a nutcase. It's because you are in a position that is wrong for you.