Check into county programs, I was able to get on the w2 program, they paid me while I was on maternity leave after having my youngest as I worked for a temp agency and also a sole provider/single mom. Hugs momma you for this!
Um by law your work place has to give you either a break or stool if needed with note from a Dr.
I would the boss if she knows the laws for that and be sure to call her higher up.
Regarding the gestational diabetes, changing your diet helps and can basically eliminate it. Please try and stay away from sugary and starchy foods, drink and fruits. Drink lots of water and try and consume more vegetables. As for your feet, whenever you can, please try and elevate your feet. Get 2 pillows and prop them up whenever you are lying down. All the best now.