Thank you everyone for your help, you have given me strength

I have contacted the priest to make an appointment rather than bring this up in confession.
I assist in my parish with both wedding preparations and annulment investigations, and the thing that concerns me the most (after reading this thread) is that, objectively speaking, a Catholic who becomes agnostic may have fallen into a state of
apostasy. I say “may have fallen” because agnosticism is a fairly ambiguous term (and people who use this term may have different understandings as to what it means to them). It all depends on whether or not your husband has completely rejected the Christian Faith.
If he has, indeed, committed apostasy then, according to
Canon 1364, this incurs the penalty of
latae sententiae excommunication, which means that the act of apostasy itself causes the excommunication (i.e., a bishop does not have to know about it and pronounce the sentence). But even if your husband has not completely rejected the Christian Faith, in becoming agnostic he may certainly have committed the sin of heresy (see
this link for the Catholic definition of heresy and its distinction from apostasy). According to Canon 1364, heresy likewise results in
latae sententiae excommunication.
The ordinary minister required to remove the penalty of excommunication is the local bishop. In some dioceses, this ability has been delegated by the bishop to his priests (at least in terms of cases of apostasy and heresy, and possibly some other cases as well). The removal of the penalty takes place within the Sacrament of Reconciliation. You said that your husband went to Confession, but one wonders what all he actually brought up. Maybe he was just “going through the motions” of Confession (while eliminating the details of his current beliefs) for the sake of the convalidation. If so, he may have withheld the information about being an agnostic to prevent that from throwing a monkey wrench into the plans.
In any event, the priest is not allowed to speak about anything that your husband brought up in confession. Your husband, however, is. So whereas I think that it is still a good idea to address your concerns to your priest, you might want to consider having a heart-to-heart talk with your husband. After all, this situation has greatly disrupted your spiritual life for the simple fact that you feel compelled not to receive Communion.
But let me also clarify that I am only speaking in general terms here. I don’t know all the details of this case, and the details are important. It could be that everything was properly handled during the preparation for your convalidation.