Winning Mahjong?

[MackySan]

[SOLVED: ANSWER AT THE BOTTOM]
I've been playing for a while and I keep coming across a hand that should be a winner but it's not?
Character = C
Bamboo = B
Dot = D
(## ## ##) = Tiles put down

4C 5C 6C 7B 8B 9B 5D 5D 6D 6D (3B 4B 5B)

Now I draw a 6D which gives me 4 Sets and a Pair left over. Which is a winning hand right? Why do I have to discard?

Edit: I just had a hand where I took a tile from another player and was left with 3C 3C (All the rest are down), but I have to discard? I only have a pair left I should win?

Edit 2: I overlooked the Yaku rule, this was my problem, I have different rules where I am from ^_^;