As someone who has ADHD… I spent my whole life not knowing – I didn’t know what was “wrong” with me, Parents, Teachers… everyone always told me “you need to focus” “you need time management skills” “you need… fill in the blank” … I had NO CLUE what they meant!! It SOARED over my head… never to return for a chance to be understood. If he kept it from you on purpose, he probably has felt shamed in the past for “not connecting the dots” “not getting it” “being dumb or whatever” — so fear of feeling yet another rejection is painful… VERY painful. You can hear the rejection before the rejection actually happens, you do what you have to avoid the rejection.
Another senerio – he may have assumed you knew. It seems EVERYONE knows the ADHD person has ADHD except the person who actually has it… Or it seems so to those of us who have adhd. Some think that the medication “takes the adhd away” – for me, it just helps with the focus… it doesn’t tell me WHERE to focus. So I often forget to tell things — very important things! I assume I have had a conversation… only to not actually have the conversation. I even can tell them what they “said”.
Basically, don’t feel slighted by not being told, or that he wanted to keep it from you to harm you, to harm the relationship. Discuss it, calmly hopefully… but discussing things with someone with ADHD can sometimes get very heated VERY fast and without any source of fuel.