Last period 03/12. last time i had sex 03/17 and 03/18. period is 6 days late with all negative test. should this be accurate by now? breast very sore. also on the mini pill?

If you are pregnant with the last sexual encounter, the fetus should be at least 3 weeks as of 4/16 so a high sensitive urine pregnancy test should be positive. Besides that you are also taking minipill and breast soreness is hardly a symptom of pregnancy at this time. I think your cycle is irregular this month but you can do a blood test to rule out pregnancy.