If you're having issues because you did something silly - it's OK to tell an adult you trust, even if it is not a parent - because everyone makes mistakes and the first step is admitting that you've made one.
That said, if you haven't done anything silly - and you are just - sick - you really do need to talk to, again, and adult you trust - again, even if it is not a parent - maybe a friend's parent - the school Nurse? Nanna? grandma? A neighbor?
Are you eating healthy and enough? If you aren't eating enough, you can feel weak and have crazy symptoms.
Are you drinking anything that might cause this? Rockstar? Amped? 5-hour energy? Mountain dew? coffee? At 14, caffeine should have a big impact on you - so stay away from all that stuff - at least until you feel better. *I recently ran into a 17 year old that didn't understand why he was so tired in the late afternoon - turns out he was drinking rockstar after dinner and thinking he was cool because he "like never needed to sleep" and he didn't realize that one Rockstar was like several cups of coffee all at once - plus sugar. I kinda wanted to bop him on the head and say - DUH really?!)
Are you drinking enough to stay hydrated? Meaning stuff without caffeine or a lot of sugar? Like water, gatorade, skim milk, decaf coffee, etc? Even kids are supposed to drink at least 4 of those disposable (16oz) bottles of water per day. If your pee is yellow, then you need more liquids. If you aren't peeing 4-5 times a day, then you DEFINITELY need more liquids. haha.
If none of the above helps, your symptoms sound a little like, it's possible you could have walking pneumonia or something called Valley Fever - which sometimes starts like a cold or the flu, but just doesn't get better. The difference between the two is that Pneumonia is fluid in the lungs. Valley Fever if fungus in the lungs and it takes a while to properly diagnose. They both decrease your lung capacity and make it hard to breathe.
Good luck. Be safe and smart and talk to someone you trust - no matter who that ends up being. :)
A site admin moved to this more general community, hope you find some help.
My original recommendation remains, but I will say the loss of sleep can cause the other symptoms of fatigue and faster heart rate.
At the age of 14 is is very unlikely you have a heart problem, not impossible, but very unlikely. That is why I asked that your post be moved.
I also believe most participants on this type community/forum are not qualified to give medical advice, only to share experience. Many, myself included, are reluctant to encourage the us of the web as a substitute for a minor discussion health problems with a parent, and as needed a doctor.
Good luck, practice a healthy life style will help I know that for sure.
I didnt know where to write this
Are there any advice though?
Please talk with your parents (or other guardians).
I hope you haven't been experimenting with anything, and also think "heart rhythm" has nothing to do with your symptoms.