Skimming your recipe--if you made it verbatim, yes, it's likely that the carrots are the 'sweet' culprit. I cannot eat onions, so I use carrot as a substitute for that flavor profile... the last time I made my favorite tomato soup, I used a HUGE carrot and could tell it was noticeably sweeter.
Try the correction Elena suggested first; after that, you might also add a pinch of salt or two to taste.
And to take it one step further, what sort of onion are you using? Here's a link to a page which might be helpful.... if you are using a really sweet onion (like a Vidalia or Walla Walla Sweet) that can also change the flavor.
http://onions-usa.org/all-about-onions/colors-sizes-seaso...
Good luck tweaking the recipe!