My problem is that i have difficulty speaking, not in pronouncing, but in producing words, where i cannot explain something or speak automatically and fluently, even in writing. i am having difficulty expressing and explaining the situation now?

It is not feasible to seek an accurate explanation or diagnosis to explain your symptoms based on data from your post. Would suggest handling this by initially seeing your primary doctor and getting referred to a speech therapist. Neuropsychological Testing may be needed to pin down the range and specifics. This can be handled successfully once the etiology is identified.