My son is 13 yrs but only 135 cm tall should I see a child endocrinologist

No, it is not safe to smoke or take any kind of drungs when you are unwell. If may have extensive adverse effects as your immunity is already low.

Yes, blood donation is good for health. Some studies have shown a decrease in Cancer risk, as well as decrease in the damage to the liver and pancreas in the long run. One should definately donate blood, ofcourse after the entire pre-requisites are cleared.

Hiatus hernia often causes heartburn and abdominal issues. In a few cases, it may also hamper the blood supply to the stomach, which is very harmful. It is best to get it diagnosed and treated to avoid such symptoms. The doctor may prescribe some medications, and in a few cases, may suggest surgery.