Husbands infertility guilt

I know it bugs my husband badly that he cannot give me what we both want more than anything. But today hes made more "jokes" about it than usual, AF is here so we know we're out this month. Its bugging him more than usual. subconsciously telling these kind of cruel jokes about himself and I really dont know how to help him or what to do about it. Besides sitting him down and talking to him like normal.. up until now I thought it was working for him.. any advice ladies ? I hate him feeling this way.. I've wrote letters after letters and given them to him to try and indirectly tap into the problem but it doesnt seem to help anymore..