Hi, I Am Taking Metoprol ER And It Seems That

Hi, I am taking metoprol ER and it seems that if I take one tablet (25 mg) then my blood pressure or my heart rate runs too high and if I take 1 1/2 tablets it cause it to run too low. I take the 1 table around 4:30 pm and the 1/2 table around 8:30 pm. This morning I had a warm feeling in the top of my head and my heart rate had jumped and blood pressure had gotten higher. I am extremely tired all of the time. What is the solution?