I think of his ex when I masturbate - how fucked up is that?

Posting anon cus I find this so embarrassing. Lately when I masturbate I keep imagining my husbands ex. I am completely straight (although do enjoy lesbian porn) and I absolutely hate this woman with a passion! I wouldn't ever want to do anything with another woman but my mind keeps drifting to this specific scenario when I masturbate where I imagine that my husband is having sex with me and that I force this woman to suck on my nipples. I think I find it appealing as I feel like I'm degrading her but how utterly fucked up is it that I am thinking of her? !