sophmurr98 Please post a screenshot or two, or a photo if the screenshots don't depict the problem.
Please also provide a dxdiag. Click Windows key-R, enter dxdiag in the run box, wait for the scan to finish, click "Save all information," and save the file to your desktop. From there, you can attach it to a reply using the paper clip (Attachment) icon included with the other formatting buttons.
Alternately, if you want to experiment some yourself, you can try installing Windowed Borderless Gaming, which is a free tool that works well with Sims 3. You'd get the fullscreen look, and edge scrolling, but (hopefully) the brightness you normally see in windowed mode.