Ladies I need an advice!!

My now fiancé and I have been living together for 2 years now, we are about to get married in a week and i Love him to death he is an amazing guy i have not a single complain about him. 
About 3 months ago my brother told me that my fiancé dated this one girl who was my brother's friend. They were together for about 9 months. Of course I know he has had girlfriends before me,but the thing is I know this girl, I hated her since day one when my brother introduced her to me, she has 2 kids from 2 different fathers, I wouldn't judge her for that but this woman is a Hoe!! She sleeps arround and she doesn't take good care of her kids, she has also slept with married men, she doesn't care any one but her self. 
This bothered me a lot, so I asked my fiancé if he stills friends with her, he said yes but that I had nothing to worry about, that  he loves me and that he would never even think of getting back with her. And he said the reason why he didn't tell me is bc he didn't think I knew her.
I believe him 100% bc I know he would never do anything to hurt me and I trust him 100000%. I don't trust her knowing how she is. Even after I talked to my fiancé this stills bother me so much that I can't help it. Sometimes when we are making love the image of him and her together crosses my mind and I haven't been able to orgasm bc of that. Idk what to do. :( Am I exaggerating? Please help!!! 😢