I Was Not Properly Taking My Birth Control Pills. I

I was not properly taking my birth control pills. I had a period, then 2 weeks later had another period. After that found out I was pregnant. I had an ultrasound that said my gestational age was 8 weeks 4 days. Because of me having 2 periods a couple weeks apart could that make my date of ovulation different then normal? And also how accurate is conception date using the gestational age?