Postpartum period

When did you ladies get your first period after giving birth I’m formula feeding and I’m not on birth control I had what I thought was a start of a period but it stopped I’ve had 6 c-sections and my twins are almost 3 months old and I have not had a period since having my twins and I only bleed for 2 weeks after having my twins why would have not have a period yet I’m not pregnant my OBGYN prescribed me medication to help me start my periods I finished them 2 days ago and still no period