Okay I’m really scared I might have lung cancer, I’m 19 I smoke cigarettes occasionally and I’ve been vaping for like 3 years, when I brush my teeth in the morning there’s darker mucus and little bit of blood in it and I’ve been experiencing a little bit of pain in my chest and and pain in the top right of my back, I’ve also been feeling very tired, I’m only 19 I’m extremely scared idk what to do.
Anuska is quite right - see a doctor.
However, at 19 the chance you have lung cancer is very slight indeed, even after a couple of years smoking. It is, however, the time of year when there are plenty of bugs about so you might have a lung infection that would need to be treated. Don't leave this, in case it turns into pneumonia.
I also suggest you take the opportunity to give up smoking and vaping completely. Smoking is known to cause cancer over 30-40 years exposure; vaping is probably safer than smoking, but no one knows for certain. For hundreds of years doctors thought that smoking was safe, and it was only identified as dangerous in the 1960s.
I should add that I'm not a doctor myself.