My Husband Is Extremely Tired All The Time. He Does

My husband is extremely tired all the time. He does not drink or smoke. He is very fit, exercises regularly and is a very healthy eater. His doctor says that he has low T and has been taking testosterone injections for 6 months, but they do not seem to be helping. He has had physicals and is in great shape. He is exhausted but has trouble sleeping and has been this way for about a year. We have had some losses in our family and have just finished building a house. Other than stress, what could this be and what can he do?