Johnny Galecki and Kaley Cuoco

`The Big Bang Theory` star Kaley Cuoco dropped a bombshell when she revealed she and co-star Johnny Galecki dated for two years while filming the show in an interview with CBS Watch! Magazine. "I dated Galecki," Cuoco admitted in the October issue of CBS Watch! Magazine. "We dated for almost two years. It was such a huge part of my life and no one knew about it." "This is the first time I`ve ever talked about it, ever. It was a wonderful relationship but we never spoke a word about it and never went anywhere together. We were so protective of ourselves and the show and didn`t want anything to ruin that. But that also made it sad, too. That`s not the kind of relationship I want – I don`t want to be hiding. We couldn`t do anything. It wasn`t as fun as we wanted it to be," Cuoco said. Cuoco wanted to the relationship to be out in the open, but not everyone around here agreed: "Certain people didn`t want to [go public,] which I understand. We knew how to keep it deep inside and never bring it on that set, ever." The couple broke up last winter and Cuoco shares that there have been some ups and downs since. "Moments were really hard, but we have such a love for each other-and we knew we weren`t destined to be together-that we accepted it and said, `Look, if we ever break up, we will be professional.` I`m so lucky it was a mutual ending and that we don`t hate each other. We`ve seen that happen on other shows," the blonde actress said.