My word, I've never heard of Dyscalculia and it makes sense in a practical manner. Looking at your post here, you've got quite a bit of trauma towards these moments of being admonished from something beyond your control.
There is still time for you to increase the capacities of your mathematical skill, but it will require a different approach. How is your imagination? Mnemonics is something you should look into for sure. I've read some people can't read clocks through Dyscalculia. I would have someone imagine Jesus on the cross. His head would represent 12 on the clock. Legs 6. Left and right arm represent 3 and 9.
Please take a look on here to get a phone consult from someone that you find from their profile:
Psychology Today UK: Health, Help, Happiness + Find Counselling UK
Please know, you're 24 years old, you've had struggles with this but you've been able to live your life up to this point. You can read and type. In the country I'm in, nearly 50% adults are illiterate.
I'm sure you have other types of talents as well. In fact, your tendencies to get distracted would be great in research. One piece of information leads to multiple sources and asking questions. Novel writing and even education. You will still have to work hard in whatever field you go into and will stumble but that is the learning process.
As for telling people, if you feel confident enough you can but I would suggest you write out your feelings into a journal. Therapy is more than the single session. Meditation, self-talks, journal entries are some methods of therapy outside of the session. If you already have a diagnosis of this you can actually ask colleges, trades and workplaces for extra accommodations in terms of time, calculators and supplies for math based solving. Through your therapy sessions and a growing mindset you can confront who you are and who you will be.
Keep on striving brother.