Babies can get cancer so yes you could have it.

Have you stopped smoking?? If you haven't then I can only sasume you have a death wish & why should your mum waste $$ getting you treatment if you won't take steps to help yourself??

If you have stopped (or do so now!!) then at 16 in most countries you can take yourself to the dr & explain your symptoms & ask for appropriate checks (like x-rays & scans) to determine cause.

Certainly sinus, coughing & breathing problems can be caused or made worse by smoking - but these can also be caused by other things - allergies (which can be developed at any age) to name just one. The coughing & breathing could make your chest hurt & you could mistake that for your heart hurting. As to your elbow - it may be totally unrelated or you may be aggravating a nerve when you cough & the nerve may link to the elbow??

Stop smoking, look into seeing a dr on your own (if you're still at school the counsellor should be able to advise you on this if your mum still won't take you).