Can medication side effect change HBP to symptomatic low blood pressure? 3 months I use same drug without problems. Last few days I feel sleepiness, diz

Yes. for many reasons this can occur (change in diet, salt intake, stress level, hepatic induction changes etc.

Yes. if the dose is too high, it can cause hypotension ( low blood pressure); there are instances where a person was not following a proper diet and was obese before but then that person decides to change his/her diet and also loose weight , causing the blood pressure to go low when taking the medication that was given before loosing weight and eating proper diet, also dehydration plus med may cause it.