I don't feel the need to come out, yet I still want to

So... I've known that I am bi for the past 3 years (I'm in year 10), and in this time I have come out to 2 people (One of which was like.. DUH!, and the other is in denial). I'm not a steriotype... well I'm more or a hybrid (I take care of my self (no makeup) and I walk and act straight). It's pretty clear that I'm gay, or at least bi; and I think people automatically assume it. So I just think coming out is redundant; but I just feel like I need to (like I'm not being myself, I can't concentrate, my relationships are suffering). It would just be easier to let people assume bc saying it won't change anything, if anything make it worse.
If I was to/ due to most people assuming, Should i just casually drop it in a conversation? Would you recommend this? or should I do it formally?
Note: I live in Melbourne (people honestly just don't care/ it's a progressive area), in a large suberb of about 20,000, but my dad is full on conservative and one of my friends said he doesn't believe in bisexuality (though he gets being gay).
Any advice helps!
Ughhhhhhhh! What do I do!

 

Thanks for the reply (sorry for the late update) BUT UPDATE, I've come out to a few more of my friends and they were ok with it, but the recent vote has made people in school (and my dad) very outspoken on the vote, with teachers voicing their point against the vote. It's made it unsafe to come out... or at least I think. Bc like everyone is making fun of it, the only few who aren't are two of my friends and one of my teachers. Since the recent vote people have also been very weird towards me, with some of the people who I thought I was close to, intentionally trying to lead me on (I over heard). This gay mentally disabled kid was even made fun of to their face, with no one careing but one of my teachers and a few of my friends. It's kinda made me feel unsafe. DO YOU recommend any LGBTQ youth groups around the city? (In Melbourne). Btw your comment really helped.
Thxxx