How to be more open? should I come out to my best friend? please help

It definitely sounds like you're dealing with some really tricky internal struggles at the moment and my heart really goes out to you (*hug*)

Let's start with the awesome thing, and that is that you sound very sure that you're gay; to be so sure of your sexuality, even though this can be quite daunting, is actually really really great! So a big thumbs up for this

I'm really sorry you got outed by your friend in school and subsequently bullied for it, this just really sucks

What makes you think girls won't ever ask you out? The only reason why they might not have done so yet is because from the sounds of it you are still really closeted; girls won't know you're interested because you keep your sexuality so private. I'm not saying you have to go and shout it to every person you meet, but no longer struggling to keep it so secret will probably be a big help. I know this is SO much easier said than done, but I honestly believe that it will be really hard for you to feel at peace if you continue the way you are.

If you would reconsider waiting to tell them, I think a good first step would actually be to tell your parents; being able to be yourself at home is a great way to start living life openly. It would also mean you can tell your best friend and not worry about your mum finding out through him.
Speaking from experience, sometimes keeping something so closely guarded like this can actually do more damage to ourselves than letting it out. I was pretty terrified the first time I came out to someone but I had to do it because the amount of pain I was experiencing by keeping it in was getting far too heavy to bear. And I'm now facing the same thing again at home; like you I still live with my folks and they don't have any clue that I think I might be gay. Having them out of the loop is getting really really hard and so I think I will tell them soon. Might they treat me differently, might they react maybe not so perfectly to this news? Yes, there is definitely this worry. But I know in my heart that the longer I keep them in the dark the more pain I will feel, and the worse it will be for me. I don't know your parents and I can't say how they will react; this is something only you have the best idea of. If they are homophobic or you think they will be quite hostile then perhaps it is better not to tell them until you have moved out. But if you think they wouldn't be too hostile about it, then I say go for it; it might not be a smooth process, and your relationship dynamic might change with them for a while, but over time they will hopefully come to see that you are still you and nothing has really changed, you just like girls and not boys.
There's a quote I read that says something like "and the day came when remaining tight in a bud was more painful than the risk it took to blossom". I think it's pretty relevant in both of our situations at the moment. x

Another suggestion would be to see if you can join an LGBT social group of some kind, just so you might get to feel a bit more comfortable in your sexuality. It definitely sounds like you are still a bit uncomfortable with living openly as a lesbian and meeting people who are living openly and happily as a lesbian might help you with feeling a little more comfortable.

I can definitely relate when you say: "However, I feel like I can’t be the person I want/need to be if I keep hiding it or even find a girlfriend for that matter."
Keeping parts of ourselves out of view to the world holds us back. Much like you I don't know what on earth I'm doing with my life and I feel like keeping my sexuality so closely guarded all the time just adds to all the things I don't have sorted out. In fact some days I think that perhaps me not living openly as gay is what's holding me back in so many areas of my life, and that once I break through this wall I have up many things will start to fall into place and I can actually start properly living.

I know it's really scary, and sometimes the fear can get really debilitating, but I really believe that there comes a time when we have to just take that leap or we risk getting so stuck and so suffocated.

Hopefully my droning on has helped you in some small way, and I really truly wish you the best. x
Please know you aren't alone in these feelings, and sending hugs your way! If you need to talk anytime you are very welcome to post on my profile wall, or reply here.