Extremely low HCG but not dropping

The only date I could have conceived was around 5/7. I do not have a cycle to base it off of (breastfeeding) but that is the only day on the last 3 months I have had sex.

Got a "period" 5/23-5/26 and then started taking ovulation tests 5/28. They have been positive since 6/2. Took a pregnancy test 6/7 and it was positive. Has stayed positive since but has not changed (has not gotten darker or lighter).

HCG 6/10 was 26

HCG 6/12 was 31

Obviously I expected it to be lower, not almost the same. Has anyone experienced this? What was your outcome?