How Can I Tell My Fiancée I've Lost My Virginity?

I lost my virginity a few years back during my service year. Before then I had vowed to keep myself for my husband, but I had a boyfriend then who eventually forced himself on me. I wont actually call it rape, because I blame myself for putting myself in such situation. He knew how much I wanted to keep myself, he still took advantage of my weak moment.

This is an action I will say I regret in my life, but I have no option than to move on with my life. I will like to state here that after that first time, no man has touched me.

Now the issue is that I will be getting married in two months time, but my husband to be (not the one who disvirgined me) thinks I am a virgin. Please I do not want to be misunderstood, I have never told him anything about it, but I don't understand how or why he assumed I am (may be because I appear to be a good girl).

Anytime he talks about it, I just try to avoid the topic. It has been difficult for me and I am confused about the situation, because I cant bring myself to telling him the truth. Do I just go ahead to tell him the truth, dont tell him at all or tell him after our wedding?

Please yours responses will be appreciated.