As a note from a man who's been on the other end of this, please be careful how much you say this to your boyfriend. Nagging at him that you aren't attractive will only make him start thinking that maybe you aren't. No one can love someone who doesn't love themselves.
Try to take a proactive view with this, and depending on how long you've been with your boyfriend, you can include him in this. Open up, tell him that you often don't feel very attractive, and you want to change that. Look for some decent books out there on self-esteem, or even better, see a therapist, even if it's just for a single session. They can often point you towards more help (ie good books and media) if you can't afford consistent week-to-week sessions.
If there's something that it would help to hear from your boyfriend let him know that stuff, but ultimately this is your issue, he can only support you, he can't fix you.
The truth is, if he's anything like I was in my past relationship, he see's all the wonderful things you are and will be, and is only too happy to be the man beside you. He just wants to be around the bright, confident man he knows you are.