Scared to lose the best thing that's ever happened to me...?

Ok so, my boyfriend and I have been going out steadily for about eight months now. No arguments, and no issues other than my over protective dad. For some strange reason i'm starting to get really paranoid, and worried that he'll get bored with me. I'm worried he'll find someone else... or he'll tell me that its best if we stay friends. Honestly there's no reason why he would, we have a great relationship...we're best friends, tell each other everything 98% of the time...I just need some advice on how to tell him this.. HELP.. I hate feeling this way..