I typically use a 7-fold and let it pop open as soon as the last part of the edge is past my pelvic bone, then turn it and push it the rest of the way in, so there's no way it's on the side of my cervix or anything. I've been doing kegels.
I don't know what to do other than perhaps try the bigger size or a different cup (except that I'm broke, lol) It's leaking so badly that a panty liner isn't cutting it. I have to use a pad backup, and a thick overnight pad at night. I can't say it's like I'm not using the cup because it's clearly catching fluid, I just can't figure out why it's leaking!