International standard weight (female) = (height cm- 100)x0.9 (kg) -2.5 (kg)
So your standard weight should be: 75.6 kg.
On this basis, the range of plus or minus 10% belongs to normal weight;
The range of 20% is overweight or thin;
So your weight is normal.
Of course, this is aimed at ordinary people. For people who love sports or bodybuilding, their muscles are very weighty.
So you may feel that you are not strong enough, so you feel thin!