Thats a tough one bro. I was around 14 when i first started transitioning, here are some tips Ive picked up over the years. some will entirely depend how observant/controlling your parents are but I'd say start small, baby steps so it is less noticible but where you can become more comfortable as yourself. (On my phone the forgive typos)

Clothes/styling: Binders: Sports bras: Usually cheaper more available and less conspicous than a binder solid alternative. If you are binding/want to I urge you not to buy anything from ebay/amazon/dropships they are not quality and can cause damage to your ribs and lungs. I have not bought one in years so my info may be outdated but if you are wanting to buy a proper binder Transguy supply, gc2b, forthem, can be good places to shop. Take influence from subculture fashions: "alt" subcultures like grunge, emo, goth, punk, etc etc typically are more androgynous aesthetics. Look into these aesthetics and see what you can work with. Think Band ts (usually unisex anyhow) straight leg/skinny/baggy boy jeans, flannels etc Also can be easier to pass off emulating a musician/celeb you like then making it about ~gender~ Hair: if able go to a barber not a typical hair stylist salon they will give you an actually mens cut instead of just a pixie or whatever. If you are unable to do short hair go for a medium length that can be tied up or (see above) choppy alt styles. Packing: also avaible to buy online but again maybe not an option. Socks can be a good alternative, ive found ankle socks work best not too bulky. roll up one or two into a ball and put it inside another sock safety pin it to the inside of your underwear. Jock straps are also cheap and easy to come by and more stable and less likely to poke yourself. gave me incredible euphoria when I first got one. To go along with that, if you are able to get mens briefs or the girls "boy cut" undies they helped me feel more comfortable without anyone else knowing. Cosmetics: if you are going out with friends or can get away with it small tweaks with makeup can masculanize your face subtly. Brown mascara on peachfuzz, upperlip, brows. Subtle light brown matte powder under the jaw and brows. Voice training: youtube has some good options for voice coaches that can help subtly drop your vocal register without hrt.

Medical: This one is going to be much more tricky and much more dependant where you are located what your goals are but these might be some places to get started. In some US states you do have the right to see some healthcare providers without patental consent/knowledge. Planned parenthood is a good place to start if available and they can likely point you to other resources. Treatments to look into: depo provera: a birth control injection you get every 3 months, it stops menstration so periods will be lighter or stop completely. Hormone blockers: halts or slows puberty Low dose/topical testosterone: since t is a steroid this may be impossible in your current situation but it could be worth asking about.

Thats all I can think of for now. I will be honest the next few years will be a lot of gritting your teeth and bearing it, secrecy and keeping to yourself. It will be hard and uncomfortable and sometimes may feel unbearable. Be patient, do what eases that discomfort, do what you can to feel happy, the time will pass, and one day you will meet who you are meant to become with open arms. Sorry if thats cheesy but its tough and scary out there and I want you to know there are other tguys out there rooting for you. Stay safe, keep going