Test still positive after ectopic pregnancy

Mrs J
It's been a month since being treated with methotrexate for ectopic pregnancy. My last blood draw was 10 days ago & it was down to 90, dr said I didn't need to get anymore blood drawn till I get pregnant again due. Hopefully this is leftover hcg from that pregnancy, I can not be pregnant again!! Hoping it's just a evap.. or left over hcg. What do you ladies think?