I Am 14 Years Old And I'm A Female I

I am 14 years old and I'm a female I have been a little constipated for a few days And whenever I poop and use The bathroom there's a little blood. But the blood is only noticeable when wiped with a tissue. It is a itchy down there. And today when I used the bathroom and I wiped with a tissue. There was a lot of blood. And it some of it was in big clots. The blood was bright red. And I know for a fact that it isn't my period. Please help me and tell me what's wrong? Oh, there is also pain down there. And it feels like it's throbbong