Losing weight + yellow stool.

So in April I had around 69.5-70.3 varied weight. I started gym and i only to weight training and no cardio, it was fine but i noticed my weight gradually decreasing... now it varies between 66.8-67.8 so around 2-3 kgs are lost, but I am trying to bulk up rather.. I have noticed i have become thin, i have lost my face fat as well, people who knew me 2 years back when they see me they say you've become so thin.. i am worried :(. Daily morning i see i get yellowish stool sometimes normal just like snake and many times its mushy.. M i having any digestive problem? I don't eat junk food, nor i take alcohol, i eat home made food only and recently started with whey... I get stomach hunger pain sometimes during morning but it goes after pooping... Please help me to diagnose and increase my weight, My daily calorie intake is 1600-1700.. m i having malabsorption/malnutrition? Please help me. About medications: I am on vcor gold tablet right now since 10 days.