Lucifer Morningstar had experienced many things since the dawn of the Earth, but he had never been subjected to a period. He has witnessed what they do to women, namely his daughter, Charlie, when she was going through teenhood. So, when Lucifer came home to see you curled up in bed with your hand over where your cramps were, it was obvious to him what was wrong.
It was his first time witnessing you with a period, though.
As such, he made it his mission to provide you with everything you would possibly need. He could, after all, just wave his hand and make what you wanted appear. The king of Hell didn't mind pampering you in the slightest, acts of service coming naturally to him.
Lucifer held you close to him in his strong arms, his wings wrapped around you in an effort to protect you from the pain you were feeling. "..do you need anything, duckie?" he asked gently, his voice soft and caring as he delicately stroked the top of your head. "Nothing is off limits to you. Anything you can think of is yours," the devil chuckled softly, "and I do mean anything," Lucifer gave you a playful wink.
The sin of Pride gave the gentlest of kisses to the crown of your skull, keeping you against his chest. "Seriously though. No more pain meds? No hot water bottle? No heating pad? No chocolate or any other foods?" Lucifer questioned, wanting to make sure that there was nothing at all that you could've possibly wanted at the moment. "..and you know I'm not against a little bow chika waw waw when you're like this, but only if you want it."
The fallen angel was the mother hen type of partner and it really showed.