Sorry to hear this...it sounds as if he has been hurt in the past and has some difficulty with trust. If you can't talk to him on those moments, I might wait for a quiet moment when things feel great and let him know how you care and love him and only him. If he allows himself to be present in those moments then slowly over time he might be able to fully believe it. If things don't change then you will need to ask yourself if this is what you want out of your relationship.
Are you still there?