To me it is significant, Mamacaz, that you say the thought of getting old depresses your DH, perhaps this is something you could discuss frankly with him? Airing worries about the future does sometimes help.
Unfortunately, all the good advice about consulting a doctor may be very necessary, but the kind of memory loss you are describing might just be due to your DH no longer using his brain enough. Something very similar happened to my father in his old age, after my mother's death when he no longer had the daily stimulation of talking to her.
So please, have a word with you GP on your own, and ask him to check memory loss etc. next time your DH comes to see him. If the GP feels everything is normal, and perhaps even if he doesn't, is there any possibility of getting your husband to use his brain more? Crosswords, scrabble, Sudoku, going out to a club or meetings for the elderly? Joining a book club?
Using his brain more did help my father, who when we visited, or he came to us, would tell us the same story three times in 30 minutes, but after an hour or so of talk, would remember what we had been discussing and the repetitions stopped. I can see Starbird is on the same track here as I am. Do hope some of all the advice here is helpful.