It's not the sizing, it's the cut.
The cut of the suit is meant to be as bland, inoffensive, conservative, and all-accommodating as possible.
-If you are getting this because you want it, then don't. It's obvious that you're unsure about your purchase and as of now, it'd be a waste of money.
-If you are getting this because you *need* it for some event, then well it's up to you. My feelings on how it looks should be clear, but no one else is going to care about the fit of your suit (despite what reading these forums suggest) so if you need it, and it doesn't offend you to wear it, then keep it.
If you want to keep looking around for something better fitting, then just keep lurking around and learning as much information as you can before you make your next purchase. Just a rule of thumb, if something "fits" you then it should be making you say "Wow hey I look good" when you look in the mirror, not "Hmm I don't know, I should take a picture and ask what people on the internet think".