You can also get the dark veins after you ovulate as the progesterone builds up in your body. In fact, for me, that was the most obvious sign that I had ovulated. I am 11 weeks pregnant now and my veins are still dark, but I noticed this during cycles when I didn't get pregnant either, my veins went back to normal after my period showed.
If you started your period on the 12th or 13th this month, it's too early to test yet. Wait until your period is late and then test.
Did you have unprotected sex? If so, the odds of getting pregnant are much higher, but I'm afraid you just have to wait and then test once you are late on your period.