hi keruru
i see what your problem is. many of us in our lives want to have or keep things that can't get together in one place. we can't have everything. it's the life's law! if you you don't forget or let him go, you may lose your lovely boyfriend!
i myself have lost many things in my life just because i didn't want to lose some other things.
he is constantly complaining that you don't tell him what he's wating to hear from you, just because you're sending him false signs! he's mistaken about your relationship but you can't make it clear to him.
the best way to get rid of this nightmare is to tell him CLEARLY that you ADORE your boyfriend and will NEVER give your heart and love for anybody but yor boyfriend. THis may hurt him both of you at first, but it will prevent future harms to you both. If he can accept this, then enjoy your friendship though i know he would most likely keep telling you the same thing since i'm a boy myself. He wants to have to at any rate!
You can tell him this, writing to him, sending him a message, etc.