Attraction towards someone else suddenly, while in a relationship
As in the title stated, i suddenly felt sexual attraction to someone besides my partner of 1½ years.
For context, so far in my live i have felt sexual attraction towards 3 people, to whom i was extremly close before. One of them was my back then best friend, another one my ex boyfriend and now my current boyfriend. All though i felt weirdly drawn to my current boyfriend while getting to know him, i only started to feel specifically sexual attraction after we started to talk every day late into the nights, about our social struggles and other deep talk. I've been extremly content in this relationship, and feel very comfortable and secure.
Now, about 2 days ago, while sitting in my break, i started to day dream a bit naughtier things. One of my classmates walkes around and when i looked at him, it just shot through me like an arrow. He seemed so desirable. I never talked to him before. Afterwards i felt immense guilt, since this sexual attraction felt as if i was being unfaithful.
I still feel attraction to my partner, but since this type of thing has never happened before and doesn't line up with my demisexuality, since i don't feel any sort of emotional bond to this classmate (he is practically a stranger) i am extremly confussed and feeling puzzled.
Now I am strongly second guessing my sexuality, and would like some opinions on this. In case this might play any type of role: he has some similarities with my boyfriend visually; i day dreamed about my boyfriend in the moment in a sexual sense; i was most certainly ovulating (and i do notice a strong diffrence in desire for my partner and libido during it). I have not seen this classmate since then, and am actually avoiding even looking at him properly out of fear from the attraction i felt in this moment (and there isn't a reason to look at him)
Update: so i felt a lot better after reading the one or the other comment, suggesting it might have been a miss fire of my brain or the overlap of daydreaming about my partner, combined with their visual similarities.
I saw the classmate again today (three days after the incident) on campus and i felt absolutely nothing, even had some small talk, just to make sure, in an attempt to understand my brain. No sexual attraction and not even an urge to get to know him, like the small talk was so forced. So I guess there wasn't even a reason to panic :)
I would also like to clarify: The sexual thoughts were about my partner. There were no sexual fantasies of the classmate, just while fatasizing about my partner a very sudden attraction feeling towards the classmate. The thought of the classmate didn't trigger the same type of attraction as I felt in that moment, and now there's nothing whatsoever while looking and even interacting with him.