Am 27 Years Old..Trying To Conceive For The Past Four

am 27 years old..Trying to conceive for the past four months..My period is due on 25th this month..i have an important function on that day..if i have got conceived i will not get my period this month.but if i didnt get conceived i will get my period on the same day which i have a function at home . so..can i take the period delaying tablet for postponing my period for 5 days?or does it affect my fetus if am already conceived? I even cant take pregnancy test because it is so early to take a test. so please help me.i dont want the tablet to affect my baby.