It's hard to imagine your thighs being big if you are wearing size 3/4's, but they obviously appear that way to you....
Do you have a few friends that you trust to give you an honest opinion? Maybe it is just how you are seeing it yourself? Do you think they are just out of shape and need to be toned a bit more?
A few things that work the legs that you could do around the house or your neighborhood: dancing, cycling, squats and lunges, walking, and jogging.