I'm 18 days late and took 2 pregnancy test that were "negative" my periods are often irregular but recently after being taken birth control (ortho evra) they have been normal for the past 3 months I have been sexually active since then. Could I be pregnant?

A blood test might be a good idea. See your doctor. Have you been taking your birth control regularly as instructed? If you miss, even just a little it can throw off your cycle.

Yes you could be pregnant. No form of birth control is 100% effective. There are many women on this site that used 3 different forms of birth control, all used correctly, and still became pregnant, some more than once.

At 18 days late it may be that it's too early to test. Some women don't get an accurate reading on a pregnancy test until they're into their second trimester.

When you tested did you use first morning urine? Did you follow the directions exactly? Most times a false negative is due to human error.

Either way it's time to see your doctor. If you are pregnant you shouldn't continue taking the pill. If you aren't, and you're not taking the pill because you fear you are, then it's just a matter of time before you are.

See your doctor for a blood test.