When I ask my husband what he thinks of what I'm wearing, he always says 'fine'! How can I get more than a 'fine' in reply? I now ask my kids instead.
I worked in advertising for many years and we considered "fine" a swear word. Fine is "just okay" and "could do better" in our opinion.
I think you need to tell your husband how it makes you feel and that you're asking him for his opinion because it's important to you, that you value it, that you want to look good for yourself and for him, and his assurance gives you the confidence you need.
Do you always tend to wear similar styles and colours?
This could be why you get the response you do: to him, what you're wearing is really no different to what you wore the last time you asked.