Nope small at the front and biggest at the back is your lowest gear. If you can't climb the hills you need to climb in that gear then well there are a couple of options. #1 get a different cassette for the back. Shimano makes a 12-27 and those 2 teeth will help a little over your current 12-25, bonus here is that the 12-27 in 10s is much more availible than 12-27 in 9s which seem to always be scarce. #2 a bit more expensive would be to buy a compact crank. Due to the fact that is has smaller rings (50-36 or 50-34 depending on what you but) you get lower gears but you will loose the higher ones. Too offset the expense you could sell your Ultegra 10s crank and BB and depending on what you sell it for and what crank you pick it could almost be a wash. #3 get stronger
well other than going back and getting a triple just get stronger, get in that lowest gear and stand up and grind it out.
Good luck.