How to pull out of depression?

I really dont know where to start with any of this... I guess you could say my depression started out 2 years ago when my mom left my dad and i without saying two words and just left, she took little to nothing with her and just left everything that was hers, here. my dad filed for divorce and started the cleaning process of getting her stuff out. (now let me just put it out there that my mom and i when i was younger, eh.. we didnt get aolng, we are both stubborn.) As my dad started to clean he found numerous things that were kinda suspicious... anyways he figured out my mom had been cheating on him... that crushed me to pieces. i could actually believe she did it.. i really could. but i mean coming to the reality was hard. anyways, Here i was 14 almost 15 by this point and i am still crying about it begging my momma to come home again calling day in and day out and her ignoring me. she didn't call me back until two weeks later to tell me her and the filthy guy she was seeing when my dad and her were still married got married.. i yelled my so loud i think the freaking neighbors could here me... i cursed her and told ehr that she was a slut and all kind of things now, looking back. .. i kinda feel bad about. but anyways, thats not the point.. they got married two WEEKS after she left.. she obviously had this thing planned out ya know? anyways.. back to the present.. where i think some of my depression kicks in... my mom has BDP, she hasn't been diagnosed but the symptoms. they are her in a nut shell. i literally cry or scream every time i talk to her because she hurts my feelings, i jsut want to haev a civil conversation with her, im afraid to tell her that im going to a therapist becasue of her actions but i dont want it all to back fire on my dad whom i care about VERY much.. more then a daughter could. my mom has gone through several im not talking to your spells where she just ignores me and acts like i dont exist and gives all her love and attention to her step daughter and acts like thats her kid.. those spells las t between 2weeks to 3months.. during that time i literally get sick, i feel like im going to throw up when i here the phone ring or if i get a text because im terrified its her and i dont want to fight. but to get to my point here..... yesterday, i get a call from her after one of her "not gunan talk to you " spells and she tells me she doesnt love me and doesnt want me in ehr life and that im not he r daughter... oh ym gosh. i kept telling myself in my head thts what she wanted to say for so long. she was crying and what not and i know that was fake, but yeah, it hurt to hear my momma cry. i mean that doesn't feel good to hear those words come from your mothers mouth.. it jsut doesn't.. im about to be 16 inna few weeks and graduating this year. i dont know what to do.. about anything. about my mom, about school, about my depression and me feeling siick all the time, i dont know. i et so weak feeling that i barely want to type a mesage or pick up the phone, i just need some advice about how to pull out of my depression im slowly slipping into. i slept like crap last nighyt becasue all i would do is cry close my eyes to drift off and feel like i was going to puke and cry all over again. i jsut need a little encouraginf i guess... sorry its so long. thanks