Hi and sorry your so tired. I agree with ChristineMP. The bp of 90/70 isn't that bad. My bp is normally around 95/58. Tiredness and bp can correlate but there are a lot of things that can cause these symptoms. Some drugs will lower your bp too. Can you give more information?
mkh9
Have you had any bloodwork done? Thyroid, CBC? Many things can cause these symptoms, blood tests are a good place to start to figure out the cause and treatment.
You need alot of rest and try relaxing more often and dont stress out.