Is 28 weeks too late for a cerclage?

So here is my back story I had my last baby at 35 weeks. I was already dilated to 5 by the time I was 27 weeks. I never had any pain. What made me go to the doctor was losing my mucus plug.. Well I have been taking Makena injections since 16 weeks. I'm 27 now and lost my plug again. Once again no pain! I'm pretty sure I have an incompetent cervix, even though my doctor disagrees. Well turns out I'm 4 centimeters dilated with no contractions. I'm scared. I don't want to have a baby this early.. So I'll be 28 weeks tomorrow is it too late to have a cerclage? I don't understand how I keep having painless contractions...