Line progression and HTC level

Emily • My husband and I have one beautiful baby girl who was born in February of 2016. 💜
I went to the doctor on Friday due to lasting spotting (5 days, still spotting) after what I thought was a period. My doc told me to talk a hpt and that was positive. My HTC level was at 23 which is 2 away from what it should be if pregnant. My lines on hpts aren't getting much darker but aren't getting lighter either. Any thought on what could be happening?