Can the white be worn during the day to the office under a blazer?

The shirt is causal style, can be worn to the office under the blazer,the shirt's collar is not firm like dress shirt's

Does this run small or big ?

Maybe a tiny bit tight across the shoulders. But I’m a small with rather broad shoulders for my size. I think a medium would have been too big everywhere else, and I will buy another Small if they ever come out in more colors. I really love this shirt. And my husband does too. Comfortable, pretty and sexy.

I’m usually a small - should I size up to look like model?

I an a size 10 and ordered a medium. The shirt fits loosely but I'd sy it 'fits' me. If you want it to flow and drop on you, then order a size up. Keep in mind you can always exchange easily for a different size. I'll add that I rally do love this night shirt and now have 2!

I’m 5’3, bust is 38d i usually wear a medium in tshirts what size should i get in this ? for sleeping

I'm a 36B, 5'6", 150 lbs. and I have this shirt in a Medium. It fits me much like the Amazon picture. You know how blouses fit your boobs but I think a Medium would work. If it isn't loose enough for you, Amazon returns are easy.