@Rosemary10,
Rosemary, perhaps as he works away from home, what ever you volunteered for he sees as a threat of you meeting other men, as he is not there often enough, perhaps it's fear.
But, 6 weeks without talking to you, he has no idea whether you took it up or let it be.. I'm thinking he would "expect" you to let it be.
He does not control your life just because you are married to him, you should be able to make decisions on your own, as long as you are not doing anything un-toward.
Having said that, what do you think his logical reason is for not wanting you to do this, is it due to the children? Where will they be if you are volunteering somewhere?
I too think there is more to this story.