Dear Lia,
Sorry for the delay but wasn't able to send the answer yesterday. It is very common that women get stuck on a certain size for a week, and then all of a sudden they progress. Every woman's tissues are different, and some stretch easier than others. I suggest you try after a bath, when the tissues are more easily stretched. Also, try doing it twice a day, and using a mirror. YOu have time, as if you practice twice a day and you birth in a week or two, that is a lot of practice sessions. You can only do what you can do, but everything you stretch is helpful for the birth. It can make the difference between a cut, a small tear, or a tear that doesn't need stitches, or not a scratch at all. Good luck