I've had three early miscarriages. In 2/3 the line was so light it was hard to see, and the third time it was a little darker but still on the lighter side. So long as it is dark enough to be detected by a home pregnancy test, you are pregnant. The usual sensitivity of a urine test is an HCG level of 50 or higher, and a blood test of over 5 HCG is pregnant (5 to 20 is pregnant but high risk of miscarriage). Early losses are common and there is no guarantee any pregnancy will stick, but a positive is a positive. When you miscarry, the levels will drop and you will get a negative test.
Me (40) DH (47) & furbabies * m/c 7/08 4/12 11/12