Bad circulation in my legs?

I think I have bad circulation in my legs. They look kind of purple, especially in winter, or red, like they do now, and my pores become really noticable. When I put some pressure on them with my fingers, they turn a normal kind of color, but then after one or two seconds they turn red again. I noticed that they look fine when I lie down horizontally, it's only when I'm standing up or sitting down that they get all ugly. They also turn really red whenever I exercise, which is quite a lot. I run 3 days a week for about half an hour, and I go swimming for an hour once a week as wel. I also eat very healthily, so I don't think my bad circulation has anything to do with my diet. I don't know what to do about it, and I'm too afraid to wear shorts, so can anyone please help me and tell me how I can treat/cure it?