pregnant again?newborn is almost 8 weeks

just had a baby 7 1/2 weeks ago Me and my husband have been having unprotected sex. I took a pregnancy test yesterday and let it sit about 20 minutes and there was a faint line. Could it be detecting hcg levels in my body from me having a baby recently or could I BE PREGNANT.

I used the same test that I used with my 7 week old and I would let those sit too.