Dull Aching Pain in Both Legs & back of knee (left)

I have been experiencing a dull, annoying, pain in both my legs since the birth of my son (he is now 5yrs old) For the first couple of years, I didn’t get it much, but now it is almost every day.
I have been to a vascular surgeon who checked my legs (with what looked like an ultrasound) and said the veins were ok and not varicosed and the blood flow was good.
He then injected the back of my left knee (the most painful part) to collapse a couple of veins he thought might be causing a problem.
I had relief for about 2 years and now it is back. Do you think I might have Sciatia as I always had back ache with during my pregnancy and still do (I do secretarial work and are therefore in the chair for long periods!)I would appreciate your advice before I go to the doctor again!