Why am I not conceiving?

My third child I had with my husband, i lost at 33 weeks pregnant due to a placental abruption. I had an emergency c section. Im 25 years old. Its now 11 months later after i lost him, I’ve been having sex on my fertile days, which really your not supposed to ttc for atleast 6 months after c section so i only count 3 months of ttc, but why have i not already conceived? I do everything im supposed to.