I should probably mention that I'm 20 years old, and a virgin. I know it's lame, but I'm too grossed out to check where my cervix is during my period. Outside of my period though, I can get the entire length of my middle finger in without hitting anything. So, now I'm looking at either the small Miacup or Medium MeLuna. The Yuuki would probably be a decent fit, but I really wanted one in a pretty color. The color isn't really a dealbreaker or anything, I just have silly priorities.
Also, I really wanted something with a decent capacity, only because I tend to be a heavy sleeper, so I'd be worried about wearing one overnight. Is over sleeping ever a problem for anyone? Would the cup overflow or anything like that?