I'm not sure if I'm reading this correctly. You believe that you love your best friend, but are not sure he likes you.
If he's your best friend, why wouldn't he like you?
Also, when you say that you believe that you love him, are you talking a romantic love or the love that you have for a friend? If it's a romantic love and you share that with him, knowing that he's not gay (I'm guessing you are....?), you might cause your best friend relationship to be really awkward. He would know you love him, yet he just wants to have a friendship with you.
Not every feeling needs to be expressed especially if you know the outcome may not be good.
I would re-think your decision to share this with him. I don't know about you, but when I become really close to someone, there's an intimacy that is shared between the two people that sometimes causes people to believe that the feelings they are having are love, when it could be a crush or just the intimacy shared.
If you are determined to share this, know that this could break the friendship you have with him, if he doesn't share your feelings and may feel like being around you would be awkward. Good luck.