Diva cup tips

I have tried to put the diva cup in twice, on previous periods. I fold it the way it says and get the cup halfway in but then it pops open. The suction seems to hurt. I'm not sure why and then I take it out to try again but it's hard to get out. I'm afraid I will not be able to get it out of I can get it all the way in. I'm not a virgin, not that it matters, I'm just wondering why it may be so hard for me to insert it and then take it out? I like the idea of the diva cup so that I am not going through so many tampons. I am wanting to try to use it during my next period, in about a week. Any tips or advice? I am comfortable putting my fingers in my vagina, I've previously had an iud and would check for the strings.