Did you have sex while menstruating? If so, the problem could be from using your cup while "aroused".

Your vagina isn't going to change (unless your hymen was still intact) from having penetrative sex. A penis isn't large enough to cause any changes in how "loose" or "tight" your vaginal walls are, but your level of arousal certainly can. When we are turned on, our vaginas grow in length, the cervix gets higher to move out of the way, and our vaginas also expand some, to allow comfortable penetration. It's similar to how a penis changes before sex. Look at a flaccid penis, and then the same penis once erect. It will be a totally different size. Some penises are "growers", meaning that there is a vast difference in size between flaccid and erect, and some are "showers", meaning that they do not change much in shape or size, but simply firmness. Vaginas can be the same way. Some of us have more "roomy" vaginas to begin with, and some may grow quite a lot just before sex.

Our PC muscles do contract during orgasm. They also do this when we urinate, or have a bowel movement. I would imagine that being more sexually active wouldn't change your PC muscles that much, if at all. Your arousal state, however, changes your vagina a lot! I could see how being aroused could change the "fit" of your cup. When I was using the SoftCup, it helped me to be aroused when inserting it, but made it harder to remove.

I hope this can be of some help.

I agree with you entirely about your main point, but there is another possibility: hormonal changes due to having lots of sex. Testosterone levels rise when you have a lot of sex:

http://www.sciencedirect.com/science/article/pii/S0018506X07000049

And testosterone levels could have an effect on the pelvic floor muscles; I remember seeing lots of discussions of this when I was researching the effect of hormones on stress urinary incontinence.

I was actually not trying to connect the cup issues OP is having with stress urinary incontinence. SUI is in part a side effect of hormonal fluctuations during the menstrual period--it seems that after ovulation and before the onset of menses, women experience it more. This is thought to be hormonal, related to the overall laxing effect on muscle tone and ligament tightness and so on. (Back pain would be another effect of this). Testosterone peaks during ovulation, too. If one's testosterone levels go up as a result of being aroused a lot and having many orgasms (yay!), then it would make sense for muscle tone to change. From my own experiences and everything I have read, pelvic floor muscles definitely do not get 'looser' from sexual activity--if anything, it's the opposite. This is just part of the puzzle.

Maybe, just maybe this has nothing to do with your bf. It seems like we all have those months when the cup just doesn't want to cooperate and we get a lot of leaking. Maybe next month will be better.

Hello, again, and I apologize for not being more clear, and also for opening up a "flood gate" of other concerns and issues. What I mean is, since I have been a lot more "active" with the bf over the last few months, I think my pelvic muscles are stronger and maybe I could use a firmer cup, since I've been experiencing leaks due to the cup getting squished. Even though I am almost certain I get it open when I insert it, I think it closes back up at some point inside me. Frustrating.

To be clear, I'm not having sex with the cup, nor is this leaking happening with the act of sex, just a general thing I've noticed, and I was wondering if the increased strength of my muscles could be folding that mc up, and I need to go Meluna Sport. Or just buy a new Meluna Classic.

Anyways, thank you for all your thoughts and comments. And yes, maybe this was just a bad month. Regardless, I couldn't go back to tampons if you paid me.

Maybe a cup with a "poppier" design and made out of silicone would work for you? I've heard people have issues with Melunas popping open because of the TPE. (I had the opposite issue--it was too firm and almost closed off my bladder. But I need super-soft cups to prevent that) - since you have a Meluna I'm assuming your cervix isn't way up there so you might like the Fleur.

I just bought a red fleurcup, thanks for the suggestion! All on sale at fw.