Are you taking beta-blockers? Most of them have an "ol" ending like Atenolol. Tiredness is their most common side effect.
If so, I urge you to talk to your doctor about an alternative. Beta-blockers have been shown uneffective and they have a lot of risks. In other words, they're more trouble than they're worth. This isn't just hearsay: beta-blockers have been discontinued for hyperension treatment in the U.K. and some other countris.
I really urge you to discuss alternatives with your doctor. You should look into natural alternatives too. Some people respond real well to lifestyle changes and natural methods like slow breathing. I know I have and I control my blood pressure totally naturally now.
If you're not taking beta-blockers it's still probably the drugs. They can interact with each other in all sorts of ways.

i have been experiencing it too, buddies of mine think its an stupid excuse for me hehehe. i also have trouble sleeping straight hours

When I was on Beta Blockers (Bystolic), I was always exhausted and short of breath. After consultation with my doctor that this was an unacceptable side effect, I was switched to an ARB, concurrent with a calcuim clannel blocker and a diuretic. I have made lifestyle changes as well. There are risks with this course as well, but I am able to live my life in a manner that I am comfortable with now. Finding the balance is absolutely individual. Best of luck to you...it is very frustrating