I don't claim to know you or your situation, so I won't pretend to. I will say that is sounds like you have some soul searching to do on your own. If's your BF's a great guy, yet somehow you feel you cannot reciprocate his love and affection, then you need to be honest with him.
Back in the day, folks used to "learn to love one another", those days are dead. We live in a time where frustrated folks end up doing desperate things for a variety of reasons. If you love him, and if you value him as a friend, then you owe it to him to be honest.
...with that said. Also, don't use this as a means to keep him on the back burner while you are figuring out what you want. It's not fair to either of you.
No matter what your decision, be strong of heart as you are in mind and body.