I recently started being addicted to pills . and my girlfriend dosent know that i am or i ever have been.?

this is a teen relationship. (17 and 18 Idk if i should tell her. i also started cutting myself again. if i did tell her about me being addicted to pills and that i cut myself. idk how she would react. please i need help. any idea how she would react if i told her? i know she would be alittle upset, but i really dont know how she would react if i told her.