What Causes Transparency To The Skin On Legs?

I am 19 years old and for the past 5 years i have had transparent skin on my legs. By this i mean you can see all the veins on my legs so my legs seem purple. My mum also has the same problem. It is difficult as i do not go out wearing shorts or dresses as people have laughed and pointed at my legs and called me corn beef?? Please help :(