Hello, dear
Your weight should be in-between 71-73 depending on your body frame and your age.
Secondly, you can definitely take they protein powder but don't exceed the limit of your daily requirement as it may cause other problems such as abnormal
uric acid level or may also cause stones.Better consult with any qualified dietician to prescribe the desire quantity of this protein powder , according to your vitals .
Third, there are many reason of not gaining weight.
. Endrocrine problems
. IBS
. Dietary problem
.
Liver problem
. Tuberculosis
.
Vitamin and minerals deficiencies
. GI (Digestive)problem
. Improper sleep
. Stress
And many more
So, if the cause is not treated then also you will not again.
So, better to consult through the link below,so that we can discuss in detail and suggest you accordingly.
Next Steps
For more information and to contact me through online /phone /personal visit: https://www.facebook.com/pg/doctorplanmydiet/about/
Thanks with regards
Dt.Ankita