Am i singing the wrong way?

You CAN use your chest voice even if you are younger than 16, it won't harm you, that's bullshit.

No, you don't expand your diaphragm. Your diaphragm is a muscle that moves whenever you breathe. It's working all the time, even when you are sleeping. You can't make it do anything else apart from what it already does because you don't have any direct control over it. I have no idea who is spreading this nonsense about the diaphragm.

And yes, you are doing something wrong since you are feeling pressure. What makes you think that you can learn how to sing through the internet? Most people on Y!A aren't even teachers so their "tips" do more harm than good. Same goes for youtube tutorials, these people aren't really teachers even if they say so. If you hear them singing, they are actually average singers. Real professionals don't give online lessons because they know that it's not safe, you may misunderstand things very easily if you don't have anyone to answer your questions. Apart from that, professional teachers have to make a living somehow so I don't see why they make youtube "tutorials" for free. Most of these people are amateurs who aren't even qualified enough to teach. Not to mention that wikihow is run by idiots.

You would rather pay a doctor to check your vocal cords for nodules than pay for a singing teacher... You ARE damaging your voice by what you are doing and you are already feeling the symptoms. I don't get why you keep doing it instead of finding someone qualified to help you. You can find singing teachers everywhere (especially bad ones) because more and more people dream of becoming famous one day.

You ARE doing it ALL WRONG and you WILL damage your throat if you continue the destructive self-learning route as you do NOT have ANY idea what you are doing.

In fact, it takes obviously some talent, some luck, LOTS of patience, diligence, courage, hard work, dedication and LOTS of lessons with a GOOD vocal teacher. Besides, your voice will keep maturing until you are in your mid-30s so you need a lot of TIME as well. Therefore:

Sorry, but THE ONLY SAFE way to learn the correct singing techniques & to improve properly IS to take OFFLINE face-to-face singing lessons with a fully trained vocal teacher! The teacher HAS TO BE in the same room with you, so that he/she can give you proper feedback. However, even the best teachers in the world cannot make wonders, so please be realistic with this. Singing lessons are NOT going to help if one is tone-deaf!

Please do NOT rely on any dodgy web tutorials because that way you can misunderstand things VERY EASILY and develop bad habits, hoarseness, vocal nodules and other nasties IN NO TIME, and even though you would sound good! It is always much wiser to invest a little bit of your money/time to face-to-face lessons rather than wasting the same amount of money (or even more!) to frequent ear-nose-throat specialist visits due to aforementioned problems, so please reconsider this. If you can't afford vocal lessons, then joining a choir is the only SAFE alternative option. And believe me, but even MANY of those who have music as their hobby DO take lessons as well!

Always remember to warm up your voice properly, but please know your limits and don't overdo your voice! Remember the diaphragmatic support, do not strain your throat too much! Also, remember good body posture!

Avoid fizzy drinks (burp danger), dairy products (mucus risk), caffeinated products (coffee & tea included, they dry up your throat) and spicy food (irritation risk)! You can consume these things, but NEVER before singing!

Do NOT shout, yell, scream nor otherwise abuse your voice AT ANY TIME! Also, please respect your vocal range; if your teacher says you are, say, more of an alto (baritone if you are male), then you ARE more of an alto (baritone).

DO NOT try to imitate anyone famous, that will usually give you just bad habits and even damage your throat. You are YOU and your voice is unique, so please learn to cherish that. The world does NOT need copycats.

Do NOT sing, whisper, shout, yell nor scream if having a sore throat/cold/flu, Also, do speak as little as you can if you have flu/cold/sore throat!

Remember to drink at least 2 litres of room-temperature still water every day, not just during singing days!

Smoking is a big no-no, as is inhaling secondhand smoke. Also, avoid staying in dusty and/or moldy environment.

The only way you are going to find out what you are doing is to go for some offline singing lessons with a qualified teacher and ask them how to sing correctly.

You shouldn't even consider using your chest voice until you are least sixteen year old. Let your natural voice develop first. Be patient. don't push your voice. The reason you are feeling pressure in your throat is because

you are not properly supporting your voice with air.

well first of all not many people can hit notes in chest voice it may not be in your range second stop doing that because you'll reck alll your voice and when you try it try and open your throat as wide as you feel you can make it if it doesn't work stick to head voice