OK, you can forget the age explanation. I'm 55 and still getting better every year. The weight gain is a possibility, although I have no direct experience with that. I however DID get a tailbone injury mid-last-season that dogged me for the rest of the season and is still making me a little tentative now (although it doesn't hurt any more). So my money's on the injury screwing with your head.
I hate the parts between winter