I have a DivaCup size 1 that I have been using for about 4 cycles now and it has been going well for the most part! I can get it in and out fine with no leaks.... after about day 3....
Every cycle I've had when using my cup I have had leaks in the first few days when my flow is the heaviest but never afterwards. First I though it would be fixed with practice but I'm using the same technique whether it leaks or not so I don't know how to stop it! Last period it only leaked twice during the first 2 days (I think) and as I'm writing this I'm on my period and thus far it's leaked one (and a half) times (currently on day 2). My flow isn't very heavy so it's not like the cup could be overflowing; on heavy days I'll empty it usually 3 sometimes 4 times and it's usually only around the 7.5ml measuring line.
Other reasons for leaks I've heard are the cup isn't open properly but I always run my finger around the cup and it's definitely open. I've heard the cervix might drop into the cup and take up room so it overflows but I don't think my cervix drops that low and even if it did it doesn't seem that would be enough for it to overflow. I've also heard that the seal might not be right but it feels the same as when it doesn't leak so I'm not sure about that one. Apparently you're supposed to turn the cup to make sure the seal is correct but I usually can't get it to turn because it's hard to hold to get it like that but I've heard many people say you don't really need to bother turning the cup. Also that the suction holes are blocked but I always make sure they're clear when I'm cleaning it after removing throughout the day so it can't be that. Or the cup might be too high or low; mine sits with the uncut stem right at the opening to my vagina and doesn't move by itself during the day so seems fine to me. Lastly the cup size is wrong but I'm a teenager and a virgin with a relatively light flow so I don't think I need a bigger size and I don't want to spend lots of money trying different cups when I don't know if that's even the problem here.
So the conclusion I've come up with so far is on heavier days there might be more weight in the cup or something leading to the seal not being very secure and leaking? I'm not really sure what I can do any differently to help, maybe keep trying to turn the cup? Can anyone offer anything that might be the issue or solution? Thanks in advance!