So I'm not pregnant?

My period must hate me because im 9 days late. 9! I've already tested myself and it says I'm not pregnant but i don't understand. 9 days though?

Has this happened to anyone else? My face has been breaking out like i do before my period but I havent actually gotten my period yet. Is it possible that my period changes with the weather? Seriously tho can that be a thing? The last 3 years, by June/July my period comes in the beginning of the month, but by December-ish my period is towards the end of the month. 3 years I've been tracking this but it doesn't seem logical? Ughh. Any advice would help!

Why am I not getting my period if im not pregnant?