Classy Date Night Outfits !

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UPDATE::: So I'm turning 18 in a couple of days and my boyfriend is renting us a hotel room to have a great night. If ya know what I mean lol 😏😂 But I was just informed that He is taking me on a really nice and classy date which he has never done . I want to wear something cute and classy . I'm a size 12 in pants and a large or xl in shirts( I'm also 5'2" so rompers are not a good deal for my short chubby self lol)  . I want to wear a sexy dress but idk where to get one . I can't order online BC it's soon. 
(I ALSO NEED UNDIES CUTE ONES WHERE CAN I GET THEM BESIDES VS )