I am 8 weeks 4 days pregnant. my periods were irregular. does an irregular period affect the conception date?

Yes: Pregnancy dating is very important so an early ultrasound is very helpful. Patients will bleed about 12-14 days after ovulation unless they are pregnant. Thus the date of ovulation not the date of your previous menstrual cycle determines your gestational age. If you have regular 28 day cycles then these two yield the same gestational age but in cases of irregular cycles all bets are off....

Yes: If you are irregular, then your conception date may not be about 2 weeks after your period, so it may shift your due date. In that case, i recur to ultrasound.