Is ligation permissible?

I am 36 weeks pregnant with my 5th child. This baby and 4th baby were unplanned. I delivered a child one and half years ago with a c section and now again it will be a c section. It will be my third c section and its getting tough for me. I have searched online a lot and found out that tubal ligation is haraam. Unless the mothers health and life is at risk. Of course if I get pregnant again very soon, my health is going to suffer and I don't want to bear the pain of another c section again. So I just want your opinion if I can go for ligation? I don't want to commit a sin in my ignorance.