I got the Diva cup size 1 because I'm still a virgin and inserting two fingers is a pretty tight fit. On light-medium days, it performs fine but heavy days are a complete failure. I currently use the triangle fold with the folded part pointed towards my back and insert it until the rim is just past the pubic bone. Then I let go and usually it springs open and sucks itself up there. I'll grip the base and give it a turn and even run my finger around the sides to make sure it's fully open and that my cervix isn't sitting outside of the cup. But despite all that, it still leaks. A lot. And the cup won't even be full.
So here are some things I've found out:
1) My cervix sits low during my period. I can get to the second knuckle of my middle finger when I bump into it.
2) The Diva cup seems just a wee bit long but that might be the stem that I'm feeling as I haven't trimmed it. It doesn't bother me that much but I'll give it a haircut and see if there are any improvements next cycle.
3) I'm not convinced I'm getting a good seal with this cup. I can push it up and down quite easily.
My theory is that my cervix takes up all the space in the cup so I'm not getting anywhere near max capacity, and I hate that. I get that I could just empty it more often but I don't want to. The whole point of making the switch is so that I can wear it for longer and essentially forget about having a period. I'm thinking that this cup just doesn't suit my body. So now I'm looking into different cups but keep reading conflicting suggestions that ultimately conclude in the only way to know is to try the cup out. But I don't have money for that nor do I want the hassle of switching until something works. Should I go for something firmer? Softer? Wider? Shorter? Bigger? Right now I'm getting maybe 2-4 hours but ideally I want at least six for a heavy day.