Hi

Try doing some exercises that work your legs independently, with the same amout of weight. If your right leg is stronger than your left, always working them together will allow your left to just "go along for the ride" and your right may do most of the work.
You can still use the leg press, but cut the weight, and do each leg seperately. Switch off the quad extension machine ( it's one of the most useless pieces of equipment in the gym for overall muscle building ) and try doing some squats- either with dumbells or a bar if you are ready. Standing on both legs forces both of them to do the work. Same with leg curls. If your gym has a standing curl machine, switch to that so that you work each leg independently. Then go do a little calf work, you don't need much, but 1 leg at a time. You can just stand on the edge of an aerobic step and hold a dumbell. Hold onto a wall or post with 1 hand for balance, hold the dumbell in the other, and raise and lower your ankle 15-20 times. Repeat on other leg.
This should even you out a bit, tho it may take a while. Also, unless you really work at it, everyone has 1 dominant side that is bigger and stronger than the other. That's why competitors spend so much time working on symmetry.
HTH,
Mel