Advice Me Please

I think.... I think I might have a crush on my boyfriends best friend. That seems so crazy to even type. I have slowly been trying to admit it to myself, but typing it just makes it seem all that more real. I have been dating my boyfriend for a year and a half. We live together, even. We talk about marriage. We also have a lot of issues. He doesn't want to grow up. That isn't bad for some things at our age , but others... He needs a real job. He needs to not make me pay for all the important stuff. Whenever we go over to our friends, 'he' is there. 'He' and I connect in what seem like a way where we could talk forever. I feel like 'he' would be able to support me and have a life with me. 'He' is more responsible than my boyfriend. 'He' has so much interesting knowledge in his head that makes me want to sit there and listen forever. We are interested in many of the same things. Well... things I used to be interested in. It's like 'he' brings out the real me that I lost a long time ago. All this and we don't even flirt with each other because that would be very wrong. I love my boyfriend. I really do. So, now what? Is this just a thing because we as humans have messed up emotions or is it real? And if it is real, there is nothing we can do about it. Neither of us would betray my boyfriend like that. 'He' probably has never even thought about me that way... or has he? I wouldn't know. Even if 'he' did, 'he' would not tell anyone because of how wrong it is. Like me. I do not ever want to tell anyone I know this. How do I just block it all out without feeling like I missed something..... ugh! Whyyyyyyyyyy?