You can still be pregnant and spot, or even have what seems like a period. It's hard to tell when you conceived if you've had "weird" periods, but if a line did not appear the first time you tested, it may have been too early to detect, or perhaps you did not conceive until early december.If a faint line appears in the window, you are more than likely pregnant. If it's very early in your pregnancy, that is all you will get is a faint line. I would wait another week or so, and re-test. If the line is a bit darker, than you know that you are pregnant. If you don't want to wait a week, call your doctor, tell them you had a positive result, and that you would like a blood test ordered just to reconfirm.Blood test levels will tell you approximately how far along you are. Good luck!