Pokèmon Platinum, Part 2

I got my fifth gym badge today. It was a bit tough, because the gym leader used water Pokèmon and I only had Infernape with a grass TM move to fight them. He did get allot of levels out of it, so it ended well. I leveled my Psyduck to 33, which made him evolve to Golduck. Now my team is pretty strong, but its only 3 Pokèmon, so I need to find a fourth one that can handle the weaknesses of the current 3. I have 2 other Pokèmon in my team, but they are only used for HM moves. Also, I finally got my Pal Pad, so if anyone reads this and actually plays this game (the odds are slim), add me to their friends roster, please!