At age 35, is there a sure sign of leg blood clot? if you have a burning feeling in back of calf for a few months on and off, but no other symptoms, is a clot possible? im thin, never smoked/drank & have perfect blood pressure. play video games daily?

What you described does not suggest venous thrombosis. It would better to engage in more physical activity, e.g., walking, rather than spending time with video games. For healthy diet: http://www.choosemyplate.gov/., exercise 30 minutes/day, drink enough water daily so your urine is mostly colorless, have safe sex, no tobacco alcohol weed or street drugs.