Don't know what's wrong! help!?

I'm 15 and yesterday or 2 days ago i started itching 'down there' and then i started my period last night while going to the bathroom but it's 5 days early! and when i'm sitting down i'm fine but when i walk it's itchy. should i be worried? i don't want to tell my mom because we don't have the money to go to the doctor.