Dear Confused Student,
You have been given much good advice on how to gracefully bow out of your study. Getting a full-time job will help.
If you become an unbaptized publisher (hopefully you will decline) you will be told how to count your time. Believe me the sisters who study with you are turning in a report on you every month. They count the time they spend with you, they count you as a Bible study, and every time they visit you they count you as a return visit. You were probably counted as a return visit when the sister took you to the emergency room and she also likely counted that time spent with you.
I, like DagothUr, became a Witness as a result of a Bible study. Thirty eight years later I wish I had had the courage to say "no".
Do not worry about hurting their feelings. You need to worry about what is right for you and your family. I am sorry that you miscarried your twins. Think really hard about what raising children in a cult would be like. For starters there are no holiday celebrations, no birthdays, no Christmas, no mother's or father's days. The only thing the Witnesses "celebrate" is a death----the Memorial. You will be expected to keep busy with "theocratic activities", ie. meetings, field service, assemblies, conventions, to which you will be expected to bring your children. There are no activities designed for children.
You did a good thing by coming here. Now listen and learn from our mistakes.
All the best,
Reopened Mind