I think the real question is: do YOU believe he's changed his ways? If you really like him, give him a chance to be the new man he claims to be. But don't be stupid. If you sense he may be messing around—and if you're honest with yourself, you know the signs—confront him. If he doesn't have a sufficient explanation, do yourself a favor and drop him. I think you should know one way or the other in about six months. Don't be afraid to dump him if he steps out of line!

Does sexual history matter? Of course! History of any kind matters. If you really want to make sure he's a good guy for a long-term relationship, pay special attention to how he treats his mom. That'll tell you a lot about what kind of partner he'll be in the long run.

Amanda Congdon is the Co-President of Oxmour Entertainment. She is a videoblogger, writer, actress and producer. She videoblogs at StarringAmandaCongdon.com and every Wednesday on ABCNews.com, while also maintaining a daily text blog at amandacongdon.com. Currently Amanda is developing a show for HBO that will feature both television and online components. Amanda currently lives in Los Angeles with her cat, Mattie, and BFF, Mario Librandi. In her free time she enjoys skiing, hiking, traveling and talking about herself in the third person.