I recieved my cup a few weeks ago. I'm 24, a virgin, and I've never been very comfortable wearing tampons. I am aware of my anatomy, however. I've done a few brief dry runs with my cup, and none have been horrible experiences.
Yesterday, I thought I'd try leaving the cup in for a little while, since I was technically "supposed" to start my period. After about 45 minutes I took the cup out and there was some blood in it. I'm using a small Lunette and it was full about until the top of the grip rings at the bottom.
I've noticed a little bit of blood (not a lot) on each dry run. The others were last week or something like that, and I didn't leave the cup in for long, so if there was more blood to be collected I didn't give it a chance. I didn't actually start my period until today, and it's usually REALLY light on the first day, so I would be surprised to see a lot in my cup if I had used it today.
I'm not sure what the source of this blood could be. I didn't continue to bleed after I removed the cup, so I'm not terribly concerned, but I really don't want to continue using it if I've hurt myself somehow.
I'm actually proud of myself for being able to get the cup in and out as "easily" as I have, and I want to learn to get used to it, but if I'm going to end up hurting myself, it's probably not worth it.
If anyone has some insight, I'd greatly appreciate it!