Do you reckon it would help if you or DH spent some time at day care, (longer drop off / arrive bit earlier and hang around/ visit for lunch) ? wondering if theat might give him bit of reassurance that you think of him during the day and will be back for him. My DD has a kids photo album with pics of all her special people that she often takes if she is away from us.

Hope you find something that helps you get back on track.