Need some work advice!!!!! Help!!!

My work doesn’t know I’m pregnant, because it’s only the 1st trimester, and we’re waiting until 12 weeks to announce. I just recently received a promotion, causing me to be needed at work more. The only problem is my promotion isn’t finalized yet, no paperwork has been done, so I’m technically training for the position. They do not have an exact date as to when it is finalized. I have my first ultrasound on the 24th, and they require a doctors note to excuse my absence. How the hell am I going to bring in a Doctors note from an OB without them finding out about my pregnancy, putting my promotion at risk because I would have to take time off when baby gets here??? Help!!