@Mountaindewed Send or fax him a written note stating that you were offended by his nurse' reaction to your sharing the news of your going back on Lamictal. Tell him that you are feeling much better, are neither high nor low, and have improved in your daily functioning (give him a couple of examples of that improvement as of lately). Tell him that your anxiety has subsided since you re-introduced Lamictal to your daily regimen. Tell him that you have monitored your skin closely for rashes and none have appeared.

Further, express your disappointment in his refusal to see you before April when you asked, and, similarly, in his refusal to discuss anything over the phone. Say that you would have preferred to discuss re-introduction of Lamictal with him and to obtain his guidance in titrating up Lamictal, but due to his dismissive attitude you were left to your own devices. Tell him that you managed well but still would have preferred to work in partnership with the prescriber and not all alone.

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He will see that you are creating a paper trail that will make it impossible for him to claim that you are a danger to self/others or grossly incapable of handling the tasks of daily living, and thus he won't send you inpatient.

If you really want to, you can simply tell him that being left to your own devices felt like being abandoned to you. If you really, really want to, you can tell him that if he does not want to provide care for you in ways that take into account your needs and symptoms, you would appreciate if he refers you out to competent and compassionate prescribers as soon as possible.

Unlike @MuddyBoots, I do not think you can quite sue him for abandonment since you have not suffered substantial harm (so there are no damages), but you can easily file a Medical Board complaint for patient abandonment against him; that requires just accusing him of a transgression, without showing of damages.