I shed about 10 pounds between last season and this season and noticed my saddle wasn't "fitting" as well as before. I could feel the sit bones in my butt much more this season. Luckily my problem was easily remedied by a minor tilt and a scooch (forward or back, I can't remember, but my knee-over-pedal alignment is still fine, and no pain anywhere to indicate a problem). My saddle was new last summer, so I knew it wasn't deteriorating. If adjusting your current one doesn't help, I'd go saddle shopping.