I'm 37 Weeks 5 Days Pregnant With My Second Child.

I'm 37 weeks 5 days pregnant with my second child. I am 1cm dialted (as of weds) and baby is fully engaged head down. I have had serious pressure on my lower abdomen. When I lay down, i'm fine, but when I stand up it's a sharp pain for a good 3mins- sometimes to the point I can't walk. I also have heard and felt a "popping" noise close to my vagina. What is this?