First of all, relax!! Be happy- you're a woman :] Now think of all the millions of women that have/are going through the same exact thing as you. Dude, you are NOT alone. And they all survived, so stop worrying sweetie!!
Everyone's bodies are different. For my first period, there wasn't very much blood, but there was a lot of brown stuff. Don't freak out if you see brown gunk- this is the lining of your uterus that has to be cleaned out every month. Even when you have had your period for a while, the amount of blood and how long it lasts will vary. Most likely it will be somewhere between 3-6 days long. Wear pads all the time and change them when they become too dirty or it's been like 5 hours. Whichever comes first. You should wear them while you sleep too so you don't ruin your pjs.
If you have any other questions don't hesitate to ask!! I promise it doesn't hurt just because there's blood involved. You might feel a weird stomach ache though, and these cramps are normal.
2 years experience :] haha