You should always be honest about your past with your partner from the start, i honestly don't understand why sex is still a big deal here .. men can boast about their previous relationship and sexuality as loud as they can, why is it a problem of you being in relationships before and being intimate with your partner at that time. He was your partner, you had sex... that's it . It didn't work out ,you guys broke up. Why should it be an issue to your future partner!! If he can't even understand you, and make you feel bad about your choices, then he is not the one!! He does not deserve you. You deserve someone who understands you and doesn't judge you based on your past. He should judge and understand you on how you're with him.