If possible you could travel to a country where it is decriminalized or legal like The Netherlands or Portugal. There might be another one closer to Belgium but those are the only two I know of. I really hope you get better.
Prolonged use of use of weed can reduce you brains motivation system which is something that people with ADHD already have a problem with. Long term use of weed may be risky idea for someone with ADHD.
source: my doctor who gave me my medical card and my psychiatrist
pirate it