I presume you haven't been in for a service in this time?
At my last service the mechanic put my seat on one of the highest positions (why do they have to fiddle?) I'm embarrssed to admit it was a couple of months before I realised! I couldn't figure out why my hair kept brushing the roof, and thought it must have been my change in hairstyle

I best take a ruler to the next service...
Other than that, is it possible it's, ahem... not the car hide but your hide... been working out recently etc etc!