The respectful way to handle it would to suggest you cooperate in an experiment, "the next time you feel this coming on." Then, if you agreed, sit with you through a migraine. And if you didn't, drop the experiment and drop the relationship if it was a deal breaker.

YES. If he really truly can't handle being with someone who takes opiates on the regular (even for a legit condition) then he can leave the relationship. If he really truly believes OP is mistaken about needing the pills, he can ask her to try going without them. But there is NO excuse for what he did.

"Testing" your partner the way he did is so fucking patronizing I would be done the second someone did that to me. Even if he had been right and she really didn't need them, that wasn't his place to dictate.

OP, he doesn't respect you. If he respected you then he would've accepted your answers even if he didn't personally agree/believe it, because it's YOUR body/health/meds. Trying to secretly test you is so shitty.