Welcome to HCM.
You have to know the basic fact that pregnancy
is only possible if unprotected sex is done or hand is inserted after touching precum/seminal fluid around your ovulation time in regular cycle.
But you say that the day was 1st day of your period.So it is safe period or not in your fertile zone.And possibility of pregnancy is nil or very minimal.
Your i pill
test may give false result. You confirm or exclude pregnancy by doing blood test
after 7 days if your period is missed.
Don't be much tensed.Wait for your next coming period.Take healthy diet.Practice safe sex