Hey SM, good to see you back
1) 5kg gain sounds OK to me, the important thing is what you think about the gain. I'd say it was significant enough, especially if the majority is muscle
2) Steriods - I'm not anti-steroids if the person using really knows what he's doing, however you really shouldn't consider it unless you've got about a decade of lifting behind you and you've reached your natural potential.
If your routine and diet is good you'll gain quick right now anyway, taking steroids at this point would just be plain lazy
3) Glad you're feeling more confident about yourself, that's what it's all about