What should I do?

My husband was recently on a ventilator for 7 days and when he came off they found pulmonary embolism. He has been a good Christian man for years he sings and plays in church really knows his Bible and lives it but since the ventilator episode all he does is cry day and night and says God hasn't forgiven him. He told me the other night that he did something when he was 20 yrs old that he will never be forgiven for (he is 71) he went out with a girl that wasn't 18 this was 50 yrs ago! I was told I needed to have him checked for dementia but he's never been able to remember anything in all the years I've known him and we've been married for 42 yrs. I am so worried about him has anything like this ever happened to anyone?