The culprit is your history

Few people, if any, has a clean streak behind them. Everyone made mistakes in the past and it's all a part of life and learning. Mostly it's just little things, but no matter how big or small it may be, it can always come back to haunt you if it lays dormant for too long. Let your partner know that you have nothing to hide from your past and if (s)he wants to enquire about anything, then they can. Relationships can turn sour because of secrets, so it's best to be honest about absolutely everything- given it won't hurt anyone emotionally or otherwise. be sensible and considerate.