A clean DTI MRI does not rule out an injury. A positive DTI MRI is very accurate but false negatives are not uncommon. A healed injury can still cause symptoms without showing the DTI abnormalities.

Maybe the language issue is a problem but the way you explain your symptoms leaves issues to consider. You come across as far more anxious than objectively aware. It is very difficult to self-diagnose most of the symptoms you have stated other than headaches. Reading about concussions can trigger an over concern for such symptoms such that every time one forgets, they attribute it to the concussion.

A professionally administered Neuro Psychological Assessment is considered the gold standard for diagnosing neurological deficits.