How old do you have to be to get antidepressants on your own?

I'm 17 and I know for a fact that I have bipolar depression. I've done a lot of research on it. My dad and many people on my dads side of the family have it. My best friend also has it and takes meds for it. I've gone to a phsycologist about it because I begged my mom to take me. They suggested I be put on some medication. My mom doesn't think I should be put on anything and is in denile about the whole thing. I know my mom won't try to get me the help I need. And I don't really talk to my dad. I'm going to have to wait until I'm old enough to get the help myself. So I need to know the age I'll have to be to get it. I live in MIssissippi if that helps.