[Coffee.]

First, welcome to TeenHelp! I (and nobody on TeenHelp) is a health professional so I can't really tell you for sure what happened whether it was a short period, a scratch, or both. Either option is very likely. As Always* said, I would talk to your boyfriend about him being more careful when fingering you. You shouldn't be experiencing pain. If he slows down and maybe uses some lubricant, that can help a lot, and if you become uncomfortable for any reason, you have the right to ask him to stop.

On the periods, it is normal to have irregular periods especially when you're young, and it is possible this is what happened. Stress and other factors (such as some medical conditions) can also contribute to periods coming and going unpredictably. When I was your age, I had the opposite problem and would have 15 day heavy periods. At that time, at the suggestion of my grandmother, I decided to try hormonal contraceptives (or birth control) to regulate my period and make it lighter. I was not sexually active at the time, and it offered me a lot of relief and predictability for my periods. If that's something you're interested in, I would talk to your parents or doctor about it! While having irregular periods is natural and nothing to be ashamed of, many birth control methods can give you more control and predictability, and are safe for most people.