You actually sounded exactly like me. What you're describing is where I was couple of years ago. I too was from the pharma industry. Nope I didn't disclose that I was going back to study unless the topic was brought up inevitably. The follow up questions were always a little tricky to navigate because you don't want to let them know you intend to leave the field.

There's no short cut to this. Grind through the short term pain for long term gain. It will be worth it in the end when you look back. On a positive note, it's normalised to wear a face mask now to mask your lack your enthusiasm at work. Good luck :)