Tilted uterus, low cervix, cup keeps creeping up past cervix opening

I had been using a soft cup for the past year, but decided I wanted to try a reusable cup and also see if it would help with my leakage problems.

I had no problem placing the soft cup and know my anatomy very well since I do NFP and check on my cervix every day. My uterus is tilted, and I've had 3 kids, and my cervix feels a little longer than what diagrams show and it hugs the top of my vagina with the opening pointing straight at my vaginal opening (if this makes sense.)

Since I've had several kids I decided to try the post pregnancy diva cup, but I'm wondering now if it's too big/too long. I get it inserted, and try to ensure the rim is between my vagina and the top of my cervix, but it feel like as I walk around, sit, etc, that it ends up sliding down and then back up below my cervix so that basically my cervix is between the top of the cup and the top of my vagina. And general leakage ensues.

Any ladies with a similar configuration inside, are you using the smaller cup instead? A different cup? I'd really like this to work. Any pointers would be great.

Thanks all!
oldgamermama