How do I help someone I love

My name is Stormie and I am 21 years old. I have a really bad problem and I really need some advice or someone to talk to. My mom is my bestfriend and I am losing her. She is addicted to perscription drugs. She goes to work and then comes home and pops pills. I hate going home and I feel bad for my dad because he has to deal with it. She won't get help. I find her problem effecting me a lot every night I cry myself to sleep, wondering if this is going to be the night that I get a phone call, saying she has over dosed. I can't deal with it, I just want to cry all the time. My friends dont know what is going on, I am scared to tell them,its just easier to pretend that I am happy and nothing is going on, but to tell you the truth, they know, that something is up. So if anyone could help me, I would be forever grateful.