"It could also be an anal fissure. This is a little tear in your anus from having a really hard poo. When it brakes open it bleeds. It can also feel like you are pooping razor blades."
You are probably beginning to have your period. It's okay, every girl has to go through this. It's apart of becoming a woman and growing up. Ask your mom/guardian to buy all the essential needs for this time of the month. Make sure to buy tampons and don't be scared to ask questions to your doctor on how these situations work. I hope this helped. :)
Should I be worried?