What Causes Recurrent Heaviness In Knee And Calf Area While Walking?

Hi, I'm 46, female, and for the past several years off and on, I get this heaviness feeling behind my left knee, calf area, no swelling, no redness, no warmth, particularly when walking. I'm not in the best of shape but trying to reintroduce my body to exercising slowly by walking. Two years ago, I had a VNG done and Neuro states everything was fine. Should I be worried about DVT?