a faint line is a line, no matter how faint it is :)
i got the same 2 weeks ago, i felt i was pregnant and took a test, got a very very very faint line, almost invisible, and showed it to my fiance to make sure i'm not imagining it :P and then i took one next morning, thinking that in the morning the line should be darker..but it wasn't.. so i decided to take a good digital test, to make sure that the faint line iS there...and the digital test said i was about 3-4 weeks :)))) and then last week, first doctors appointment... the line was darker....so you can wait a week, the line will be darker :) but you're still pregnant :) congratulations :)
First of all congratulations! To recieve the news of pregnancy is always fantastic and exciting!
If you feel that you are 4 weeks along then the control line on your pregnancy test should be nice, clear and dark! However if the line is there then there is almost a certain chance you are indeed pregnant.
To be certain though I would pay a visit to the doctor where he can then confirm it for you and the celebrations for your up coming baby can begin!
May you be blessed with a healthy baby and good luck!