I work as a waiter and often do 70+ hours of walking on the job. i also smoke and eat poorly due to the job. now im having heart palpitations and my knee is constantly in pain. what checkups should i do when i next see my gp? what should i be wary o

Leg pain palpitation: Would get EKG for the heart palpitations and check thyroid function, magnesium level, potassium level calcium level. general blood count ,CBC and metabolic profile CMP . Stop caffeine- energy drinks as causes palpitations . Stop smoking. For the knee pain have you tried motrin/NSAIDS if not allergic? or Biofreeze ( do not apply more than 2 times a day as you get absorption)? Get xray/MRI

Palpitations, health: For palpitations - ECG and an event monitor/Holter monitor depending on how often they occur. Also labs to include- thyroid, electrolytes, blood count (CBC). Depending on what the palpitations turn out to be, may need an echocardiogram to look at heart structure. Stopping smoking will be the best to reduce many future medical problems. Knee needs GP eval since many possible causes. Best wishes.