How do you dress “business casual”?

I usually wear khaki-like pants (usually ones that are black in color but khaki texture) and sweaters. I always feel like I’m underdressed and worry about looking unprofessional....

But when I try to dress up more at work I’m just so darn uncomfortable that it genuinely makes me less productive. I attempted to wear a blazer with a dress and tights yesterday and I just could not even stay comfortable sitting in my chair 😭

Not to mention also, my office is always FREEZING, so a nice blouse or something is never even an option because I’ll need something to wear over it anyway or be shivering all day.

Ladies who are supposed to dress “business casual” for work what do you usually wear??