even if the line is faint it means you are PREGNANT for sure.Beta HCG blood test will give you better results
the same thing happened to me, I took the test 1 day from a missed period, and it was positive, I took the other one 4 days from the late period and it was negative, but I could feel that I was pregnant, but a strange thing happened when I got my period 10 days later with severe cramps, and I was thought to have miscarried, so I would advice you to go for a blood test