There is no such thing as “a little bit pregnant”, so if you are seeing double lines, even if it's faint, then your body is producing human chorionic gonadotropin (hCG). This hormone is detected in the urine during pregnancy. So why is the line so faint?
One reason is that different brands of tests have different sensitivity to the hCG. There are tests that are able to detect the hCG as early as five days before your period is due. There are others that you should only use after the day your period was due. Check the box of the test you are going to buy to see how sensitive it is…the lower the IU/L (milliInternational Units per Liter) is the more sensitive the test. (If you want more accuracy, a kit with 20 IU/L is better than a kit with 50 IU/L).
Another reason you may be getting a faint line is that you didn’t have a 28 day cycle that month, and you aren’t as far along as you thought. Your average 28-day cycle is split into two basic phases: the phase leading up to ovulation, and the phase leading up to menstruation. If your cycle is irregular, this could have been a month that you ovulated later than day 14, and there fore you are more newly pregnant than you thought, and your hCG levels aren’t very high yet.
If you’ve had a faint line for a few days, and then the line disappears entirely, you may be experiencing a very early miscarriage. You may have had an egg fertilized, but for some reason, the body detected a problem, and discontinued the development of the embryo. This happens in any where from 30 to 40 percent of all pregnancies. When this happens, the majority of women don’t even know they were pregnant.
So, if you see a faint line, check again with a sensitive test in a few days. If the due date of your period has passed, and you are pregnant, your body should be producing a normal and detectable amount of hCG. If the line becomes darker, Congratulations!!! Be sure to visit your OB right away for confirmation by blood test, and for an early pregnancy exam.