So I've only used cups for one and a half cycles and I'm still not sure about these things (about to buy a yuuki cup). When I've had them in while sitting or really just "being" I feel air escape. Like it feels like blood escaping but I check and there is none so it's air. So.. what does that mean? Is this supposed to happen? Does it mean it is being crushed? Does it mean it is the wrong size?