How long now?

Went to my 38 week appointment today. She checked me and I'm dilated to almost a 4 and I'm like 90 or 100 effaced. She also said my baby's head is EXTREMELY low... I think she sweeped my membranes. I'm cramping and spotting and getting bad pains in my lower belly. How long till something happenes if it's going to? And what are my chances with how effaced and dilated I am.