Welcome, I'm so happy you found us, but so sorry you are dealing with anxiety at such a young age. Stick around and we will try to help you along this journey, we do care and above all else we do understand anxiety.
It sounds like you are dealing with health anxiety, many of our members also deal with health anxiety myself included. You're first step is trying to believe the doctors, you have had heart test and they told you that your heart is fine, you must try to believe this. I know it is hard, but it is the first step to recovery. Secondly, I recommend you see some type of therapist, for mindfulness or cbt therapy which are both proven to help with anxiety. You can see your regular doctor for a referral to a therapist.
I'm going to post some links on health anxiety, please take a moment and look them over. And remember you are not alone, we are here for you so post when ever you'd like.
Health Anxiety - A Self Help Guide:
www.nhs.uk/conditions/hypochondria/pages/introduction.aspx Helping health Anxiety
www.cci.health.wa.gov.au/resources/infopax.cfm?Info_id=53 Health Anxiety- The Super Scanner
www.get.gg/docs/SuperScanner.pdf