He has to break his curse before she breaks his heart.

Good Luck Chuck

Cursed since childhood, dentist Charlie Logan cannot find the right woman. Even worse, he learns that each of his ex-girlfriends finds true love with the man she meets after her relationship with him ends. Hearing of Charlie's reputation as a good-luck charm, women from all over line up for a quick tryst. But when Charlie meets the woman of his dreams, he must find a way to break the curse or risk losing her to the next man she meets.