It depends, if it's a secret that you think will impact your current partner, he/she better find that out from you and not from other people. Also, all secrets will be revealed in time, it's just a matter of timing. So then better reveal your secret if necessary, only if it will help in the improvement of your current relationship. Reveal it in proper time or in good ambiance, when your partner is in a good mood then you will see that the impact of revealing a secret is not bad at all, based from my own experience. Cheers.