Two years is a long time to ignore something like this. You could have developed hamstring tightness too. You can try the following exercises: Stand upright with your feet wide apart and your hands on the hips. Push your bottom back, then pivot forward from hips, with your back straight and chest thrusting forward. Then drop your hands well in front of your feet. When the pull is felt at the back of your knees, hold for 20 seconds. Breathe out. As the flexibility increases, move your feet close together. Repeat at least twice. Try to get your legs at right angles with your back bent. Then keeping your back straight, try to place your chest over your straight leg. When a pull is felt at the back of your knee, hold for 20 seconds, breathe out. Repeat at least twice. Do not force this movement. If you are very stiff, grasp the back of your calf, and pull gently forward. Also, lean backward in line with the straight leg, to stretch the muscles on the bent leg. Do not lean away from your bent leg. If later walking does not produce pain, slowly increase your walking routine. You can try swimming too to relax your hamstrings.