I assume - You had bleeding, 10 days after Mifprane tab. After bleeding stopped, HCG
test was negative. You had sex after 5 days, that is 15 days after your 1st day of your last LMP - exactly in the ovulation period. 3 weeks after your sexual contact HCG is positive. That is 15 days + 3 weeks, which is the 36th day from the 1st day of your Last LMP. Now the HCG test is positive. If the assumption of mine is correct you are pregnant now.
Usually Mifprane tab is taken as abortifacient preferably between 6th and 7th week after last LMP. Confirm your days of pregnancy
and if your pregnancy is within 7 weeks - and if you don't want this pregnancy, after consultation with a dr you can take abortifacient tabs carefully.