Drug Test Results Question

I have not smoked in 19 months and decided to smoke a good amount during the evening of 10/5/12 through the evening of 10/6/12. I took a first check drug test on Sunday night which was 24 hours after the session and there was a line next to control but no line next to drug. I assumed this was positive. However i just took the same test 2 days later tonight and there was a line next to control and a very very faint line almost like a "ghost line" next to drug. I had my friend look at it and he confined it was a very faint "ghost line". Please note the test on Sunday there was no line not even a "ghost line" So my question is am i barely above the 50ng threshold and will i have a more distinct negative test within the next day or 2?

here is a picture, if u look closely u can see the faint "ghost line" line next to Drug
Let me know what you guys think, thanks!

http://i45.tinypic.com/2lnu6o1.jpg