Abortion Pill-Pregnancy test after positive?

I had my daughter 3 months ago. Last month I started my BC and had sex with my boyfriend (To be safe I took Plan B as well). About 4 weeks after not getting my period on the day I usually get it (which I thought I'd be off due to hormones, BC, and Plan B) I took a pregnancy test and it said positive. I went to clinic the next day and took the abortion pill. Last week I went back for sonogram and they said they saw nothing but I took a pregnancy test at home and it was positive. Do you think the test is positive due to hormones and hcg levels?

*Lesson learned btw*

First accident Ive had with my bf of 9 yrs.