Yes, post some photos first so we can work on the solution.
The 550D/T2i is a very popular and capable camera. I used to own one. Great photos, pretty much on par with my 7D. What the 7D can give you is a lot more options (which it seems at this point you need to avoid), to increase the chances of shooting more CHALLENGING scenarios successfully compared to the 550D (higher fps, much more sophisticated AF system, more durable, more weatherproof construction, etc.)
It is highly unlikely but possible that your 550D may need service (calibration), but first we have to look at your photos and I'm sure it will come down to settings, improper usage etc., no offense 


