Since these symptoms have been going on for 6 years, you should definitely get them checked out by your primary care doctor
to make sure there is nothing serious going on. You should especially seek urgent medical care if you are having trouble with bowel or bladder control, or significant weakness in your legs, as these can be signs of a more serious spine problem.
Back problems would be the most common cause of symptoms like the ones you describe, although they usually occur in people much older than you. Spinal stenosis in particular is a narrowing of the spinal canal which can compress the spinal cord and which causes numbness
and pain in the legs which is worse with standing for long periods of time but often gets better with sitting or leaning forward.
"Blood problems" meaning problems with the flow of blood through the blood vessels in your legs is also a possibility. Again, given your age, these problems are unlikely, but if you have diabetes, if you smoke, or if you have high levels of blood cholesterol it is certainly possible.
Start by making a visit to your primary care doctor, who will give you a thorough check up and help you figure out if something serious is going on.