19 weeks pregnant with a varicose vein - freaking out

I am 19 weeks pregnant and this is my 3rd pregnancy. I weigh 130 and haven't gained any weight so far this pregnancy. I've been working out by jogging on treadmill and eating right. So WHY do I have a couple of bulging veins on my left calf!? I didn't have this before pregnancy. They look like a bruise. So depressed