I'm with Amber, it's really weird. I just stopped caring about my SR too. Not to get all tin foil, but I'm convinced that the game drives down the SR of older accounts to keep them playing. (I know I'm better than this, better play one more game!)
I mean, my peak was 2850. My current SR is 1850. Every season, I drop about 100-200 SR lower than I was during the previous season. I'm either slowly getting worse, or something is up. But like I said, I stopped caring about it.