what is love?

i know he loves me back && all the nice things he says to me are true but the thing is what am i scared of. Is it the fact that knowing that maybe one day he wont feel the same way about me.Ugh there is just this weird feeling inside of me that does let me express me feelings.There is something seriously wrong with me :| i know i love him && without him my life would have no meaning but when it's time to tell him how i feel i just freeze. i hope he just doesnt get the wrong sign. One of my big problem is that i'm super insecure does any one know how to fix that?