weird lump thing on my vaginal lips

hi im 15 years old and im a girl i have this weird lump thing on my vaginal lips and its not a pimple well to me its not but i started geting it 2 months ago i got it before my period and once i got my period it went down then i got it again before my period once again it went down, a week after my period it came back so i left it because i thought it would go away again but it hasent and its starting to hurt iv tryed searching it but i cant find what it would be but im 100% sure its not a pimple and i havent had sex ever in my life so i really dont know what it is

please help me im to shy to tell my father and i cant tell my mother because she isnt here so PLEASE help