8 lorene,

Welcome to my blog! I am going to answer your question first since you are new to this forum. You said:

That is a big difference between “increase your pain IN” and “increase your sorrow AND.” How do you explain the difference in translation?

The NIV is not a word for word translation but a thought for thought translation. It is what the translators thought that God meant that is shown in the NIV. However the original does not have “IN” childbearing but “I am increasing grief of you AND pregnancy of you” You can see the original Hebrew words with the word for word translation here:
http://scripture4all.org/OnlineInterlinear/OTpdf/gen3.pdf

There are two things that God said he would greatly increase – Eve’s grief (meaning work or labor) and her pregnancy (meaning conception). Eve’s conception would be increased because she now is mortal and humanity must still be able to fill the earth even with death in the picture. Her work (grief) would also be greatly increased because of all the work that would result from all the pregnancies that she would have to endure and how quickly she could now become pregnant since God said he would “greatly” increase her conception.

I hope that looking at the original Hebrew with the English translation will help you out with understanding God’s meaning.