Would a test show up positive if it was 21 days ago i had unprotected sex n just spotted one morning the day i was supposed to have my period?

Blood test: It could, but to be certain you should request a blood pregnancy test be drawn.

Most likely.: Hi, Pregnancy tests are very sensitive now. Some have very accurate results as soon as 6-7 days post ovulation. So, if you had unprotected sex at or in very near proximity to ovulation and considering that the period is consistently about 14 after ovulation, then using a home pregnancy test would be a good thing to do since enough time has passed for there to be a very accurate test result.