How do I make myself do it?

I've already posted on here about how I feel like I need to come out to my mother about my sexuality. We are in this weird limbo of her half knowing and shes never gonna accept it that way. I suppose I will be saying I'm bisexual, thought I'd like to make it clear that my feelings for girls are sorta stronger.

Anyway, I'm pretty sure she doesn't quite beleive in bisexuality and she sort of dissaproves of lgbt quietly while not actually being straight up homophobic... She also has little respect for my opinions/plans/independance etc. So I'm just sort of afraid she will find my coming out slightly funny but also slightly worrying, like I'm doing something stupid again.

But, I'm not afraid of being thrown out or violence and I really want to come out so I can just express how I've been feeling. You see I've been doing badly at school and when people ask me about friendships and extraneous reasons that might be keeping me down I don't know what to say without outing myself. I also just want to be able to tackle her annoying mildly homophobic comments towards me without having to excuse myself so I don't have to admit my sexuality.

So, how am I supposed to just make myself do it? I came out to my best friend because I hinted for a long time and then he asked me... I feel more scared about coming out to my main friendship group because I've crushed on two of the girls who are now together and I know that them just suspecting it has cause some tension in the past. I had a whole text conversation with my very liberal older sister in which I told a long story while expertly not getting to the point because it involved my feelings for a girl. I'm really not one to talk about emotions. But I just want to you know it feels unhealthy. So I feel like I need to do it. How do I make myself do it? Maybe not even my mother but someone. Me and my best friend had a fall out and now I have no-one.