State law differs regarding DBA publication. Generally speaking, when publication is required, the DBA statement must be published once a week, in a specific newspaper that posts legal notices, for four consecutive weeks. Publication is included in the LegalZoom filing process.
If you are not having a period or you are having an irregular cycle, you can still get pregnant because ovulation occurs before your period, and ovulation can restart at any time. Young women can even become pregnant before their first period. There are no concrete physical signs of ovulation, so you could be ovulating and not know it.
I have a 3 year old from that very thing. And yes, in rare circumstances, women have been known to ovulate during their periods, so if you are asking if you could be pregnant from sex 3 days into your period--yes to that also, but much more unlikely. As for the suggestion to go to the doctor for 'morning after' contraception--please don't take that advice.