Aneros won’t stay in

I bought this:

and it simply won’t stay in. After a few seconds of hands-free use, it slides all the way out until only the tip of it remains. Then depending on what I do in terms of relaxing/contracting, it slides all the way out. If it doesn’t slide out, it just sits at the tip and kinda falls down to the right against my thigh.

any advice? I also can’t find my prostate for the life of me.