bad period cramps

so i’m only 14 and i’ve had AWFUL periods. i got my first period over a year ago and at first they weren’t bad at all but soon it just all went downhill. i got awful cramps where i threw up non stop and blood was everywhere like a murder scene. it was also all over the place. the longest time i had a period was about 20 days and it was ROUGH. and it seems to just be getting worse and worse and i do cheer and this is really holding me back. i asked my mom abt birth control and she refuses and says i’m way too young. i also feel like she thinks i’m just saying it so i can have sex with my boyfriend which i don’t want it for that reason. i just need some advice on what to do