Girls only please- What is wrong?

Please help- I'm 13 years old, and I started my first period on the 20th. It was pretty light at first, and then became rather heavy on the 21st. However, by the time I went to sleep on the 21st, it had reduced to a light trickle, and (I thought) was gone by the next morning. Just earlier, though, I discovered that I had been bleeding again, and changed my pad, but now there is no blood! I'm unsure of whether or not this is normal.