What's wrong with your current typing speed? It's more than people usually
have. Do you feel it drags you down for some reason?
I don't think any of your colleagues considers it a problem that you type slower than them, and to me, faster typing is more of a party trick than a necessary skill.
Of course I understand that my comment here may not ease your mind in the matter if you happen to want to actually type faster (as opposed to wanting not to be burden for colleagues). Unfortunately, I can't offer you much of an advice, barring maybe seconding the howlett's comment about looking a word ahead of your current position.
[&] Now that I think of it, the speed of following is probably much more on the side of me not knowing how to pack more precise information and my thought process into sentences than anything else.