worried!?!

so your girl hasn't had her period for two months. i haven't fooled around and i haven't had sex recently but there are some days i don't remember what happened. my boobs are tender and hurt when i run, do jumping jacks, etc. i can't be pregnant because i haven't had sex but i don't know what the reason for the couple of missed periods? i'm also a little bloated. if it helps anyone out eve says my risk of pregnancy is 9% not much but still scary. to put this in a worse perspective i'm at a good age to have a baby, in still in high school. thank you to anyone and everyone who has read this far, please comment on what is going on if you know.