I managed to increase my weight from 87kg (form 5) to 100kg (end of diploma) in 3 years without any supplements. Just eat more food. MOAR and MOAR.

168 cm

a lot of course, not at your level

I'm just showing to TS that he doesn't need supps to gain weight. And that's my weight at 2010. Now, it's lower and at lower bf%

Haha. I know man. Didn't intend to mislead at all

Obviously you can. Just don't make a mistake like I do once where I managed to get my weight to 100kg. And my little piece of advice, don't be too attached to the weight. Unless you involved in any sports that have weight class, then weight is important. Other than that, aim for a good muscular body. Maybe you want the beach body kinda a type, maybe you want a little bit ripped.

My lil bro at 172cm have a 75kg muscular body and that's an awesome body.

yeah. mirror is the best indicator to show whether your diet is ok or not. If you aim for weight loss/weight gain, you had to rely on weighing machine and not all the loss/gain is good (like your situation and mine). Just take it slow, make your gain as a good gain