why does it make me angry when my bf says i'm beautiful?

K, so I've been dating this guy for 2 months. I'm a pretty good judge of character and this guy is genuinely nice. Everyone I've met thinks so and I tend to agree with them. He's never asked me to do anything I don't want to. He tells me to go at my own pace and he's okay with that. He wants me too. He's lived up to his word thus far and I don't see him turning back on it.

So now that we've established that this guy is nice. My question.

why do I get angry inside and almost fed up when he calls be beautiful? I've never really gotten this way when other people call me beautiful or had this reaction.

Or he will call me a pretty lady and things like that but instead of feeling good about the compliment I just feel angry as if it's an empty compliment which it doesn't seem like at all cause he's all smiles and giddy when he does say it.

Not to sound conceded or anything but I happen to like the way I look and know I'm good looking. I also am in shape. I run marathons and exercise regularly so it's not like i'm out of shape.

This is my first 'serious' relationship. I'm 21 he's 23 and we've known each other for 4 months.

But I just want to know why I can't take a compliment from the guy!

What are you're thoughts?