Faint line 7 days after period?

Had what I thought was first postpartum period the 22 - 26. Been nauseous this week so took a test this afternoon & am seeing a faint line. Not super faint in person, clearly there, pink, and full line within no more than 5 minutes of testing, but not fully convinced because was just on my period?

Do I just schedule an appt with my doctor if another test today or tomorrow shows positive, or do I need to be going to the ER in case of threatened miscarriage?