Blood in urine can be due to many reasons. But the most concerning is the possibility of cancer in the bladder
or the kidneys
.Other causes are urinary infection, enlarged prostate, due to the aspirin, stones, and benign lesions.However the most common cause of bleeding at this age is from an enlarged prostate and urinary infection.
Smoking is a high risk factor for bladder cancer , hence you need to be more vigilant about these incidences.
Ideally you require further investigations -CT scan of the abdomen, Urine exam and cystoscopy( seeing inside the bladder with a camera).
You have symptoms like pain, frequency and difficulty passing urine, which are signs of an infection. So there is a chance that this is due to an infection only. But there could be exceptions. Clots represent that the bleeding is significant.
I would advise you to see your doctor immediately who can order the necessary tests and confirm the diagnosis for this bleeding.
If it is the enlarged prostate, then medications will take care of it. If it is infection, then antibiotics will resolve it. If it is the aspirin, stopping it for some days will do the job.
If any mass or cancer is detected then it require treatment according to its merit.
I hope this helps you take a quick decision.