Terlupe last date period

Assalam sis, sy nk tanye... cmne ye klu sy terlupe date last period... tp tanda2 pregnant tu ade... ni skrg tgh pregnant ank ke4... sy takut sy salah kira... sbb jarak ngan ank no3 da 6thn... mase g check kat doc... doc kate ikut kiraan da 6w mase tu... tp tu laaa xconfident ble nk g bukak buku pink nanti & nurse tanye nanti ...