I have a few conditions as well, such as add and I'm on the low spectrum of aspergers autism... It can be hard for me to learn certain things, so sometimes I need something repeated in a different wayThis. I'm all for not giving your age out online but in some circumstances people knowing you may be younger or have mental health considerations may help people to communicate in a more useful way.
My oldest son has ASD and I can quite well imagine him having similar conversations and responding in the same way when he was younger.
I have worked with children from primary age up until adulthood. Sometimes people just need a different approach but if you don't know that it can feel like your bashing your head against a wall.
There is nothing wrong with being young or having mental health considerations, nobody here is going to bash you for it. At the same time you shouldn't feel that you have to declare these kind of things either.
Just in this case a lot of people have been trying to help you and the response they have received has made it harder and harder for them to want to do that. Hence people questioning your age. Honestly they are much more likely to hang in there and try and help if you are younger and inexperienced other just being an adult who doesn't want to listen.