Hi i totally understand how you feel i was addicted to smoking and later vaping for about 2 years from the age of 14 and I also went through a ridiculous amount of puff bars etc.
In my experience the only way to really be able to quit is by truly wanting to. I thought about quitting for a long time before I actually committed to it and the first few months were very hard. I found that it really helped to focus on the benefits of quitting rather than how much i missed smoking - because i did, and still sometimes do long for a cigarette, or to use a friend’s vape etc.
Whenever I spend money on clothes or books i think about how i wouldn’t have been able to if i was still funding my addiction, and i try to focus on how freeing it is not to get withdrawn when i cant smoke etc because my body is so used to being without nicotine. Its also really great not to worry about lying to the people around me or having them worry about me - and i feel somewhat superior now to everyone else who still thinks its cool to vape, regardless of how ethical this opinion is, it really helps me to stay clean!
Quitting nicotine can make you very upset or cause you to feel unwell, so if you think you will have adverse effects, or be too focused on nicotine rather than revision for example, wait until after exams to quit.
Best of luck, and if you would like more support i can pm you?