I'm not a doctor, of course, and I don't want to alarm you, but your husband could be in the early stages of a serious neurological problem, such as dementia or Alzheimer's disease. The first thing you need to do is bring this to his doctor's attention.
Even if it can't be cured, his doctor can help you learn to cope with the problem and point you to resources that could help you. Many communities, for example, have social service agencies dealing with the problems of older people. Share your concern also with your children; they need to know and may be able to help you in practical ways. Don't be ashamed to ask for help; you shouldn't carry this burden alone. The Bible says, "Carry each other's burdens, and in this way you will fulfill the law of Christ" (Galatians 6:2).
No matter what his diagnosis is, ask God to help you be the kind of wife your husband needs today -- just as you've been in the past. Instead of rebuking him for not remembering something, be patient, gentle and kind; rebuking him will only upset him. Remember: If he does have a medical problem that's impairing his memory, he can't help it.
May this also be a time when you both grow closer to Christ, and discover afresh the hope we have in Him. Old age can be hard -- but God is faithful, and His promise is true: "Even to your old age and gray hairs I am he, I am he who will sustain you" (Isaiah 46:4).