How did that happen and when?

With nothing better to do I started going through some of my 100,000+ photo files. The files are not all portraits or family photos, some images, such as those of cars and boats, Art and Artists, etc are included in the number. I have a collection of selfies as well and all dated. Those photos are the most troubling as I can see myself aging in those photos. But, that is not what really scared me, it it's the fact that I can't remember when these photos were taken. Yes, they have dates, but the date is meaningless to me. I can't remember back to February of this year but from that date back to mid year of 2021 is gone. 

I used to be able to use my daily journals to remember things that didn't come to mind right away. But I stopped my journals at about the same time so there was no help there. I still remember bits and pieces of the missing 2 years, but they are too shallow to help me capture the whole memory of what was happening that day. At some point I lost the ability to balance and now I depend on a 'walker' to keep me upright. It's also obvious that I lost a lot of weight during those years. How did that happen and when?