Nothing can get stuck in your vagina, what goes in has to come out and the length of the unaroused (it becomes longer when you’re aroused) vagina is approximately 6 to 7.5 cm (2.5 to 3 in) with your cervix at the top so there is no where else for it to go. Millions of women insert menstrual cups, tampons, sex toys and other objects into their vagina, they very rarely get stuck, when they do a woman can easily remove it and in very rare occasions can go to her doctor or hospital to have whatever object is stuck removed. The menstrual cup tends to stay very low down in your vagina, lower than a tampon, it has a ‘tail’ that you can use to help remove it but you don’t need it as all you need to do to reach the cup is bare down – using your vaginal muscles to push it closer to your vaginal opening. You would always be able to reach it with your fingers so always be able to remove it.
If you are experiencing pain when inserting anything into your vagina than it might be something you want to talk to your doctor about as you may be suffering from vaginismus – where your vaginal muscles spasm or tighten causing pain during penetration. This is normally psychological, in other words you worry or have issues with things being inserted into your vagina. It may however simply be that you are tensing up as you’re not used to vaginal penetration, in which case I would suggest masturbation as when aroused your vagina becomes longer, wider, more relaxed and lubricated, it’s natures way of making sure that penetration is not painful. Lubrication is another idea, such as KY jelly or olive oil – remember too that a menstrual cup can be used any time of your cycle, not just during your period, so you can practice for a while before you use it during your period, you can also use them in the bath and shower so use the water as a lubricant and to help you relax.
FYI menstrual cups aren’t just silicone and aren’t always bell-shaped, there are different types of menstrual cups, in fact you’ve listed a few of them. Reusable menstrual cups only last up to 10 years, 15 would be pushing it a bit.