You and I are the same age; I was diagnosed at age 60. You are not too old at age 69: you may live for 25 or more years, and you cannot give up on yourself. Doctors certainly know that people often have depression and ADD at the same time, and you may be running into resistance by doing self-diagnostics. Your challenge may be in getting effective medications rather than getting a formal ADD diagnosis.
You may be expecting too much of yourself in view of having lost your husband recently. You don’t say how long you were married, but if you spent 5 years caring for him, you are heavily invested in your relationship with him. It is just not realistic to think you can grieve him and regroup in six months.
An ADD diagnosis helped me in the sense that I could understand that some of the crazy things in my life were in fact due to a real illness. It took some time to arrive at a good mix of medications for ADD with anxiety. Medications are helpful but they are not going to cure your illness or solve problems by themselves.
Try to start small. If you are living with someone, make sure you keep yourself neat and clean. Do some of the small jobs that make the house pleasant and make an effort to make the household run smoothly. This won’t require money. Try to see what needs to be done and make an effort to be helpful without being prodded. You may feel better, and your welcome may last a lot longer too.
Try to believe there is hope for you, because there is. Good luck.