Welcome to HCM
You have hogh blood pressure, your occupation is trekking guide, If you feel heavyness in the chest it may have cardiac or Lungs problem,for wich you should get a ECG done as soon as possible and if it is normal,may be you get a narrowing of airways that is asthma
like for which Atenelol 50 mg may not be suitable drug.Even Pulmonary function test may be done to know the bronchospasm
.Also at high altitude Oxygen
is less may cause chest tightness
it would also be advisable to check Haemoglobin
level are you Anaemic?
Go for medical check up once cause is known you will be alright soon but continue to take your BP medicine keep BP to 130/80 mm of hg level. decrease salt in diet.