Hi i'm beyond stressed

about a  month or so ago i noticed a small fatty lump along my breast line at my right breast,it can be easily rolled between my fingers , i was worried but it was close to my period and i was beyond busy and times passed and its still here and i havent done anything and i know its so so stupid but i havent had a chance to breath and now im in my last year of school and im beyond stressed. 

i have too keep calming myself from big panics but im terrified and i know i need to tell my mum or someone so i can get it checked out , but im so scared, what happenes if its really bad and i do have something wrong , i know its rare when im this young but idk and im in my last year of school and im stressed.

its usually not painfull , sometimes especially this week around my breast have been annoying me , but i've but that done to my period just ending. 

please help in just need some adivce, how can i tell my mum without sending her paniciing, and i dont know when to say it like obviouly i know now but the gps not open till monday whicih would leave two days of panicking and i have so many things happening in my life a the moment and this is all so franctic but im terrified , that maybe i've left it so late something bad has happened or maybe its just period/hormones and nothing at all .

please please please any help would be appreciated!