I was prescribed this drug for HBP and have been taking it for 6 ...

I was prescribed this drug for HBP and have been taking it for 6 days. I've been checking my BP daily and it is now on the low side, averaging 100/60, sometimes lower. On day 2 I tried to take my dog for our normal walk and was so fatigued I could barely make it home. My legs were burning like never before! I thought that my body might just need a few days to get used to the medicine. However, I have become increasingly tired and the muscle fatigue is so bad I can't even blow dry my hair, or scramble eggs without my arms burning. I also have developed a slight cough. I took 1/2 pill today but think I will stop after feeling like this and reading all of these posts.