I don't feel pretty enough for my boyfriend?

Do you guys or girls ever feel a little insecure or feel like you are not attractive enough for your significant other?
I'm not sure why for the last couple of days I have been feeling like this a lot. My bf briefly mentioned that a mutual friend of ours said his ex gf was pretty (she said it at the time they were together but he mentioned it a few days ago). I think this made me think about it a lot. I'm not sure how she looked like but It just makes me wonder if I'm even pretty or if he finds me attractive? Sometimes I think I should dress a little better or wear more make up. I also wear glasses and am skinny and sometimes I feel like I'm too skinny and maybe he wants more curves? (I know he tells me that he's never been with a girl my size) I'm not sure but I feel my self esteem is low at the moment :( how do I feel better?
Also I've been dealing with some health problems lately and feel depressed about it.
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And sometimes I fear that he wouldn't care if he lost me because he could find someone better.
I don't feel pretty enough for my boyfriend?
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