greetings from healthcaremagic.com
I am Dr Sourav Chakraborty and i will be helping you with your query.
First of all do not panic and think sensibly , worrying will make you more tense .
You are only 18 years of age and the syptoms you have mentioned though very limited is significant. You have not revealed your mom's details which is important for your case. Does she have murmur since childhood or got it lately due to particular cardiac ailments. Different type of cardiac ailments can give rise to murmurs but their pathology is different. Also the origin of murmur is also different. Mitral valve prolapse
can give to mitral regurgitation
/ murmur and if asymtomatic is serially monitored cautiously , but mitral regurgitation due to myocardial infarction
and Rheumatic heart disease
needs promt care and management.
Going by your age and without further details from your side i would consider structural heart defects atrial septal defect
or heart rythm abnormailty as a differential diagnosis in your case. Please do get a baseline ECG and a Echocardiogram
with doppler study done at tge earliest for if you have murmur , other abnormality it can be easily evaluated.
Also we need to rule out other co morbid lung conditions if any and hypertension
which can present with sypmtoms similar to your case.
I firmly believe you need to visit your doctor at the earliest, hope i have been lucid in my approach . Take care.