I've just started on doing bodybuilding, following allpro's guide into the third week now. Have some questions to ask.

1. I'm 172 weighing at 80~81kg. For the past 3 weeks it had not exactly gone down. Why is that? Muscle gain? Or just fats that's refusing to leave the body?
2. I'm doing barbell with 20kg weighs mostly. Do I include the weight of the barbell itself? Or does the weight includes the extra weigh that it comes in? (dont' know what's it's called, round dish on the sides) I'm trying to log my progress.
3. What's a good motivation to carry on with the regime? I'm on the third week and frankly I think I need some motivations to continue on.

Thanks for the help.

This is recipe for disaster. You are not having a good diet but you are starving your body from nutritions. Guess you might be proud losing 2kg every 4-5 days without needing to even do some exercises. 

It's not the nutrition that makes you fat, it's the calorie and yeah, you did said you eat a one meal a day and drink milo and water. Sure, I really wish you'll success to get that 60kg but bear in mind, you are losing a lot of muscle mass with your current diet. Prepare yourself to be not able to eat much because of scared of gaining weight.