I’ve definitely worried about that but if you’re making progress you won’t lose it in between! Don’t worry!I have slept with the #4 on a number of consecutive nights though, I think if you feel comfortable doing that go for it. I worked my way up to #4 and it’s completely comfortable in me now, so I leave it in longer than usual. That is also because I have minimal pain and anxiety though so you will know yourself better than anyone. You will surprise yourself though! I went 4-5 days without dilating for my period and was able to insert the #4 immediately after with no problem! Do what you’re comfortable with, but don’t worry about losing progress. If you do have to go down to #3, try putting it in for an hour and switching to #4 right after, or after 30 mins.