Short Term Disability (CA)

Since becoming pregnant the back pain symptoms and anxiety have been 100x worse than they ever were. I have been having to leave work early almost every day because by the end I can't stand enough to even get to my car. I'm out of sick time now and my job of 11 yrs has suggested I go out on STD since they aren't able to accommodate me anymore than they already have. I asked my OBGYN and she was adamant that she would not put me on STD. She said "a lot of women have back pain during pregnancy and work on their feet" she referred me to my primary care who gave me a note for work to avoid long periods of sitting (which is what is aggravating my back) my WHOLE job consists of me sitting at a desk with customers. I'm 100% not ok to be working. Half he day I'm crying in the bathroom because it hurts so much and I don't know what to do anymore. How can I get my STD benefits that I've worked for? (I'm 23 weeks) after the baby is born I get 12 weeks full pay from my job and it would not be from disability.