Not necessarily but you might be. How do I explain this..? I am not cisgender, meaning my gender doesn't align with my biologigal sex. But I don't consider myself transgender. For me being trans has more to do with dysphoria, a feeling of not being at home in the body, mannerisms, clothes, etc. that are expected of you. So, in your case, I would consider you trans if you feel uncomfortable when wearing girly clothes or if you consider your chest too big or if you hate having to put on make-up all the time. But if you are totally fine with your body, your clothes, being girly,... then you might still be a demigirl (because gender and gender expression don't have to line up either and it's your call what feels demigirl to you) but not necessarily trans. Just like your gender, being trans is something only you can define for yourself and if your definition of transgender is just as simple as "not cisgender" then that is entirely fine as well. I just think the term transgender wouldn't add any new meaning if it were that simple because by specifying your gender you have already specified you're not cisgender (unless you are the "classic" mtf or ftm perhaps, but that is usually such a strong change that dysphoria is pretty much a given).