War gets rid of your rationale. The overwhelming emotions cause you to act impulsively and different to how you usually would in order to survive and cling to those you also hope to live.
That's how you got into this situation. You have no idea how though, it was just a few times, a few days, and then when everyone returned home to Velaris you two were distanced once more, awkward and unsure. Perhaps that was your fault, you were embarrassed of what you had done with Cassian, you had no regrets, but he just made you shy and once the adrenaline from the war was gone, so was your confidence and so you had begun to avoid Cassian like the plague. You didn't acknowledge the desperate passion you two had shared just after the victory and almost death, only your thoughts clung to the pleasure.
But now, by some misfortune you were late. You thought fae struggled with fertility, that it'd take years to conceive. After being turned into fae 7 months ago your cycle had been completely messed up, you didn't understand it anymore, but your period hadn't come in 8 months now, and you doubted that was normal, even for fae. So now terror consumed you as you pondered over the thought of confronting cassian and navigating this confusing and overwhelming new life as a fae while also possibly navigating the chaos of motherhood.