The color of the line is insignificant. Pregnancy tests can only tell you if you are pregnant. The darkness of the line is no indication of how pregnant you are or how far along you are. You can use the brand tests, even from the same box and get a lighter or darker line any time.
The phantom calls that you have recieved, also known as ghost calls is usually caused by either a poor quality phone line, aka has a high amount of noise or foreign battery due to the line or your on an older copper line.
Telephone companies offer another service known as Last Call Return. When you get a call, you can hit *69 and you'll get the last number that called your phone. You can then use phone reverse search to track down the caller and his or her address. This method, as well, may not always work for cell phone numbers. If you use a cell phone, try this little trick.