Why would my bloodpressure go from 118/78 to 136/83 after i take my second dose of nebivolol. it only last for just over an hour. i take 1 in morning and 1 in evening?

Blood pressure normally varies widely during the day and with physical activity, emotion, and other factors. Anti-hypertensive drugs like nebivolol lower BP on average, but not every measurement is below or above a particular number, no matter how long after a drug dose. Both BPs you report are normal and not harmful. Discuss with your doctor if you remain concerned.