Would you break up with someone if they had trouble with expressing their emotions towards you?

So, I'm quite possible the worst girlfriend in the world. Every time my boyfriend says he likes me or something remotely romantic I'm just like, "Oh cool. Me too." in a monotone voice. I'm pretty unemotional when it comes to relationships, not because I don't like the person but because I've just always struggled with expressing how I feel and end up coming off as cold or uninterested. So basically 50% of the time I'm with my boyfriend I'm worried he's going to break up with me for being an unemotional freak, even though he knows I really do like him. Pretty much had to vent that.