You don't have to tell them anything, unless you want to. Since it is causing you difficulty, go to the equal opportunity office and you can get your doctor to fill out a form qualifying you as disabled through the Americans with Disabilities Act. With that registration, that is all you need to tell professors. IIRC, they can't demand specific information. The ADA office will work with you to determine what you need to help you get through school.

The catch is that it can't give you an advantage over other students, it is meant to put you on the same level as everyone else, which you are not right now.

My anxiety issues made it really hard to complete tests on time, so the office was able to get me extra time on testing. I also got extra time for assignments but rarely needed it. I can't tell you what a relief it was to know I had that to fall back on if I needed it. It is the office what determines what you need and the professors have to follow it.

Not only does it give you legal protections, it saves you from having one professor deciding you get one thing and another deciding on something entirely different. I didn't know about this law, until I asked a math professor for more time on tests. He told me he couldn't unless I got an ADA exemption, so it is likely if you go straight to the professor, they will direct you to the ADA office anyway.

Since you are in grad school, telling your advisor specifics can be helpful. It was very helpful in my case. It took me 2 years to complete my thesis and project after my coursework was done. It should have taken me 6 months. To save me money she was able get tuition waived for the required 2 credits needed to be able to work on my thesis and get face time with her.

It really depends on how close you are to your advisor and how understanding you think they will be.