What to do if my husband just informed me that he dropped me from his health insurance policy?

When the divorce action was filed, the Court should have issued a Temporary Order.  One of the provisions is that neither one of you cancel any insurance policies.  You should bring this to your spouse's attention immediately so that he can reinstate your policy.  If he refuses to do so, you need to file a Motion to Enforce the Temporary Order immediately.  Although the judge may order that he reinstate your policy, the insurance company may not be able to do so.  In that case, you should ask the Court to require your spouse to pay for the new policy until you get divorced.   

As a general matter, the law does not require a spouse to take employer-offered health insurance at all; or if he does, to cover his spouse and/or the rest of his family.

If you are in process of divorce, if the open enrollment period were still open, it is possible that a court would grant injunctive relief--a court order--requiring your husband to reinstate the coverage on the grounds that he should not alter the status quo while the terms of the divorce are still being worked out. However, if open enrollment is closed, that may not be possible--while the court could issue an order against your husband, directing him to take advantage of something which is available, the court would seem to not have the right to force the insurer to offer coverage when the open enrollment period is over. The pending divorce between the two of you does not affect the insurer's rights, obligations, business, etc.

It is worthwhile for you to consult with your family or divorce law attorney about this--and if you don't have an attorney, you should get one immediately; clearly, this is a contentious divorce, and you want to make sure you protect your and your daughter's rights. However, you need to be prepared that under these circumstances, you may not be able to get your coverage reinstated.