How can I lighten/shorten my period without birth control?

There really isn't any way to do so.

As you get older your period will become more regular, and likely shorter. I'm guessing that you're a young teen that's just starting this stage of life. It can take a few years for our bodies to get into the swing of things.

As for flow, there's really no way to make it lighter. The pill can help regulate you, but most times it will not actually change the flow rate, and if it does, it won't be a huge difference. It is what it is. Your body is unique, and your period will be unique as well. There's really no way to thwart mother nature.