Right Leg, Front, Whole Quadricep Muscle Area Extending Down Into

Right leg, front, whole quadricep muscle area extending down into the whole front or face of the knee, occasionally goes SLIGHTLY beyond knee into shin, but not usually. Very significant "ACHE" & discomfort, bordering on pain at times, not sharp or burning pain, it's intermittent, not constant, feels better when I sit & take a break, not bothered in bed or off my feet, have been bothered for two months or more, has become more significant & frequent the past month, can't tell for sure, but feels like a muscular issue. Over the counter pain relievers not really helping.