Goodmorning 40C-OG,
I understand how you feel. Being a 40C, a bra is necessary. You have every right to feel comfortable and supported and present with a more attractive shape. I dressed for the office for years wearing my bra underneath a button shirt or ladies blouse. I usually wore a camisole under my top.
I'm a little bit more busty and couldn't do anything about disguising my front. For me, when I was still pretending to be a man, I made little to no effort (like most women) to hide what I was blessed with.
You can do things that will help hide your bra outline like your band and fasteners as well as your straps and adjusters. However the little bumps on your back help give you the comfort, shape and support that you need to get through your day. I never had any issue or even a negative comment when I wore my bra as a man at work. I did however get empathy from the ladies that I worked with and even shared my story about how and why I started wearing a bra.
Good luck and be proud of who you are and what you have been blessed with.
♥️Sophie♥️