|Are you old school?|
Most typewriter fonts are called monospaced fonts. That means that every character takes up the same amount of space. It made sense using two spaces after a period because of the size of the letter and gave you that visual break that you needed. Now, no longer working on typewriters, most computer fonts are proportional fonts which means that letters are different widths. Single spacing is more logical. Chicago manual of style, the APA style book and the modern language association all recommend using just one space after a period.
Check out Grammar Girl Quick and Dirty Tips:
Check out the article on NPR News. At the bottom you will see a paragraph that explains the "rule" of spacing after a period.
Another good article is on About.com: