Don’t be dishonest to your lover, don’t lie to him or her that is a sure timebomb planted in a relationship, even if it is pure heaven damage will occur when that bomb will explode.
It is better to lose a probable relationship by telling the truth than losing a wonderful relationship just because your past was exposed.
I always follow that policy without regret. Well, after my return from hell one of my cyber-friend was suffering from an illusion that he was in love with me, I simply told about that part of my life in clear words and why he should better be looking for someone else, he did not believed me of course, but I told him anyway. He drifted with time, but had he been insisting I would have sent him a copy of charons, the story I have written about that time to tell him what he was inviting in his perfect life.
Now, telling truth is not always easy but it is always wise!