Phases tend to last for less than six months, and then you move onto something else. If this is something that has resurfaced repeatedly throughout your life, it may be worth talking to a counsellor to investigate it.
Many (but not all!) of us do realise early on that something isn't quite right, but we don't fully understand what that means until several years later. In the meantime, it's pretty common for us to do our utmost to fit into the role everyone tells us is the right one for us - especially if our families are unaccepting. In your case, you were told you were a girl so you tried your hardest to do that. So did I. You know why? It's because we're human, and humans crave the love, acceptance and support of their families, so we'll do everything we can to make sure we stay in their good books. But living a lie can be hugely self-destructive, and we can only take so much before something has to give.
A key factor for many trans people is puberty: everyone finds it awkward, but for trans people it can be hell on Earth. For me, when puberty hit and I started to grow curves in all the wrong places, it felt like my body was betraying me. I became depressed and deeply embarrassed about showing any aspect of my body to anyone, lest they see how female it looked.
If any of this sounds familiar to you, talk to your folks about seeing a reputable counsellor. As you're still in school I presume you're underage; if so, you'll need their permission - both for a counsellor and for potential blockers/hormones. If you're not underage, can you see your GP and ask them to refer you to someone? Or perhaps there's a school counsellor who might be able to help?
Ask yourself this: how do you see yourself in 10 years' time? In 20? In 50? Can you imagine yourself in a retirement home, wearing a chintzy, flowery dress and sensible shoes, still having people address you as 'she'? Would you look back on your life, having lived as a woman for all of those decades, and be okay with that? If that sounds doable, then you're fine to leave things how they are for now and see how you go. But if that sounds like the stuff of nightmares & endless regrets... speak to a counsellor as soon as you can.
