I (F22) don't feel enough for my boyfriend(M24)

Whenever I see pictures or videos of beautiful gamer girls, my heart drops. I know he'd look at them and find them so incredibly attractive. He's very briefly mentioned it before.

He used to say I was too good for him and I would reassure him, but now I feel so insecure and not good enough for him and I have a bad gut feeling.

I hate this feeling so much. It makes me so anxious sometimes that I can't function normally throughout the day.

Any person going through this, how do you deal with these emotions?

(I have tried bringing this up to him before and he has reassured me but the dread never goes away)