If the balloon is slipping too deeply inside, then you can let some air out and pull it out. If it is more than half inside, you are not stretching properly the entrance to the vagina, which is the part that usually will tear. You MUST have the largest diameter in the entrance of the vagina, so thaTt you have to hold the balloon in or it will pop out. If the balloon stays inside by itself, this means it is in too deeply. When you start getting to the big diameters, you can cause small tears when the balloon comes out because you are not stretching the entrance as much as the inside so when the balloon comes out it is painful and can tear. The measuring is meaningless if it is not in the right place. You should not feel pain when the balloon comes out. In the ninth month there is lots of yellow and thick discharge so if there is no blood, it is not the mucous plug.