Lucerys might've lost you forever, the realization dawns on him with fear. the tears pricking your eyes make him swallow ― make him feel sick at how much pain he is causing you, by simply standing there, next to Baela...

his short trip to King's landing to defend his claim on Driftmark was supposed to be nothing but that ― a simply political matter in order to secure his spot as a lord of Driftmark, and not have his uncle Corlys Velaryon become such instead, as his brother Jacaerys was already in line to become his mothers' heir, Lucerys was supposed to rule another land.

he had left you at Dragonstone, and with a kiss to his forehead you had wished him good luck, and he had promised to return successful of his duty. however, when Luke did return, successful, yes, but not because of him simply securing the spot as a future lord. his mother Rhaenyra (as much as he loved the woman) had proposed for Luke to become betrothed to Baela, to further strengthen the alliance between Targaryens and Velaryons. it had been the final ploy to convince Rhaenys to let Luke become lord, once time was right.

at the moment, he hadn't really thought about the compromise to take Baela as his wife, as only much later, he had realized that it meant his mother would then send you away, as he was now officially betrothed, and any promises to your family were therefore undue.

so when he came back, a feast was quickly held, all in favor of the future lord and his much too early announced betrothal. Luke didn't even have time to tell you privately, to explain himself properly..., he just had to hope that you would understand that this was never his choice to make.

not that he could really change it, right? this was his duty, after all...