How sick to get disability leave

I have HG and am 21 weeks. At about 13 weeks my OB offered me a week disability but I was trying to be tough and passed it up. At 15 weeks I asked for it over email (she had told me to ask if I still felt bad) and her response was it is hard to claim and let's wait and see if I got better given I was in my second trimester. Well I'm not better (though I do have some days where I don't vomit as much). I'm losing my strength and feel to weak and sick to go to the office every day. How do I get my OB to realize how much I'm struggling?