So confused

Is it possible for breastmilk to come in 1 week later even though im not breastfeeding? My breasts have never been hard, I tried breastfeeding my newborn at the start but i could tell that she wasnt getting enough so i got her on formula (she was hungry every 5minutes). I was just about to get in the shower and as soon as i took my bra off my nipples started leaking white, I dont know what to do if I should get her on the breast again, the first 3-4 days have been so stressful I dont know if i want to go through that again.