OK it sounds like a new chainring is the go...
You need to find out what bolt size/pattern your existing chainring has, i.e. four or five bolts and what is the Bolt Centre Diameter (BCD). Once you have this info, either go down to your lbs and ask for a 46t chainring with that bolt pattern. Or search the net.
There is a special tool for holding the back of the chainring bolts, it only costs a few bucks, but you may be able to manage without.
Finally, the 22 tooth limit of the Shimano triple front derailleurs is really only a guide, you may be able to go a little larger, possibly a 48t, but this is just a matter of trial and error. Also, the bigger you go the longer the chain will need to be, I would guess that going to a 46t won't be a problem with your existing chain, but it may be. Chains aren't all that expensive.
A good source of info is always www.sheldonbrown.com