Get on with your life & forget it! A death's always stressful when you know the person, that's probably what causes your anxiety. If it continues to concern you then get professional help from your Doc. who will advise you. Best of Luck.
Please accept my condolences for your loss.
What you are experiencing is extremely common, and normal. When we are dealing with the loss of a loved one, it brings our own mortality into sharper focus.
The death of someone we love is unquestionably, in my opinion, THE most stressful life event we must all endure. And that stress can manifest itself in countless ways, anxiety being very close to the top of the list.
While I can understand that this recent loss has caused you concern about your own heart health, know that it is EXTREMELY rare for someone your age to suffer a heart attack.
While you didn't exactly say you have a history of "anxiety," you did say that you "have a bit of a history of always assuming the worst and getting worked up about health problems." I think you probably have a mild case of health anxiety and this loss is simply exacerbating it. It's good that you're aware of this.
The symptoms you've described are far more likely to be related to gastrointestinal upsets due to stress. Our guts are often the first system to be adversely affected after a tragedy as we either don't eat well or we don't eat at all. Extreme stress causes more stomach acid to form which can cause bloating and gas. These in turn can cause the pressure you're feeling in your chest as the stomach pushes upward. Your burping is your bodies way of trying to ease that pressure. That is why it is important to eat something even though I know you don't feel hungry. Putting something into your stomach will help absorb the acid and reduce the gas. Even if you can only manage some crackers, it's better than nothing.
So, the answer to your question is that I DO think this is health anxiety, more specifically, HEART health anxiety.
As I said earlier, it is very uncommon for someone your age to have heart problems, to help you deal with this before it becomes an anxiety "disorder," I would suggest that when you are feeling up to it, see your doctor for a complete physical and be sure you discuss your health anxiety........your doctor really needs to know about this issue. Talk with him about possibly getting into some therapy to help you deal with this. If you are having any grief issues, the therapist can also help you move through the stages you will encounter.
Because you are so young, you may never have lost anyone before......the grieving process can be rather frightening and intense. To help ease this journey, you may want to Google the 5 stages of grief so you will know that all your feelings are normal.
Take care of yourself during this difficult time. See your doctor when you can and may the winds of peace enter your heart.
Blessings
Greenlydia