This is actually quite urgent and you need to get medical attention right away! I mean now, and not tomorrow or the next day. Anything that affects your breathing in that way needs to be investigated. It could turn out to be something like the beginning of a chest infection but you do need to get your lungs and heart checked out to be on the safe side. It could also be something like asthma, but it is impossible to say on the internet exactly what it is as you need to be examined. Please, for your own sake tell your parents and ask them to get you to a doctor today. It is concerning that you have this feeling of pressure on your lungs and this needs to be seen to. You need a few simple tests, examination and some treatment. Good luck
** I stress again, do not delay in getting to a doctor.
You need to go to the ER.
Please get urgent medical advice – go to A & E now.