Major need, 'more gears' as the undulating route of 15 miles was tough on me and I am useless on hills - I just didnt have enough easy gears -
As Tony said, you might need gears with a lower range. Your local bikeshop will be able to suggest something and do the work for you.
One other thing you might like to try is changing down earlier and spinning your legs faster. Less force per revolution but faster revolutions is easier. Might not be enough but it'll make a difference until you get the new bits.
