I feel tired, have back ache, and my doctor says i have blood in urine?

Hematuria: Those symptoms aren't good. Could be an infection in the bladder or kidneys or could be something else. You will probably need to see a urologist sooner than later. I hope the first doctor also examined your urine or drew some blood for signs of infection and considered putting you on some antibiotics.

Concerning: Blood in the urine is most concerning. Your age and tiredness and backache just add up to the picture and warrant further work up.