i'm taken and is limerent to a coworker who's taken too

i honestly am very disgusted with myself because of this.

i (24F) have a boyfriend (22M) for a year. i also have a coworker (24M) who's been with his girlfriend (24F) for 8 FUCKING YEARS. i've been working with him since December and i became limerent last June.

he always made a pass on me through borderline flirty messages and actions. my boyfriend and closest friends are aware of this. he was naturally funny and goofy that i never took any malicious intent until just last month. they bothered me because he's taken, and i would tell him to stop the flirty banters but it would still pop out of nowhere.

he would always say how pretty i am. yesterday, i showed a photo of a baddie coworker from another department, and he said "the more i look into her photo, i realize how much she looks like you." BUT SHE DOESNT LOOK LIKE ME. he then described the similar features we have, and how we're both pretty. this also happened when he complimented another coworker's looks because she "looks" like me.

other times, he would offer me food, coffee, ask the most random things. he also offered me a crocheted penis gift during valentines (as a joke) but i refused to accept it. (it was hella weird) when our team went to a trinket store, he wanted to buy something then i asked "for your girl?" and he said, "no, for you." he told me that i was his happiness (LMAO). during our team building, he reached for my hand and retracted it.l immediately. his mood would also change/drop if i compliment other male coworkers' looks.

he also admitted that if he was single, i would be his crush.

i'm disgusted that this turned to limerence. that im now enjoying his attention. when he's actively posting his gf, i would feel a drop on my chest. if we were both single i wouldnt want to be with him anyway. i feel so guilty for my boyfriend, but ive always wanted to spend more time to be with him but he's studying medicine so our time is very limited and it makes me sad and very alone.

yes, i have also planned telling this to his girlfriend, but when he told us that his gf doesn't care when someone flirts with him, i didnt know how to approach it. i am also actively setting my boundaries but not to the extent that he would wonder why we stopped talking. i am keeping it professional but he would always find a way to talk about personal things.

i want this to stop but i cant -- my brain is wired to crave dopamine so badly. i have been too traumatized growing up and was deprived of the good kind of attention. i am so tiredddd of this (i was also limerent before) and im scared that this would affect my current relationship moving forward.