Thank you for your query.
If you did not have any preceding illness or exposure to certain drugs or radiation
you have either idiopathic (cause not know) pericarditis or viral pericarditis
(which may or may not be part of illness myo-pericarditis. You were treated with ibuprofen
that is drug of choice for pain of pericarditis. So far so good. Now you have started becoming out of breath with a little exertion and becoming lightheaded both mean that your heart is not acting as an effective pump to push blood forward and therefore there is congestion in back that is in lungs, therefore you have lightheaded as a result of former and breathlessness as a result of passive congestion in lung veins. That signifies your heart muscle may also be involved and now not been able to contract effectively. Due to forward flow not adequate with the need of brain make you light headed and as if you are going to pass out. Passive congestion -back logging of blood- pulmonary veins(veins from the lung to heart) makes you short of breath.
You have to consult the doctor who would arrange for an echocardiography
for two things amount of fluid in your pericardial sac and contractility of chambers of heart. You will need bed rest
. Fortunately in most cases the disease is self limiting.
Dr Anil Grover