The Dreaded Plateau!

I've hit it. After losing 102 lbs (so far), I've been stuck at 256 lbs for the last 2 1/2 weeks, fluctuating between 256 and 262. Yes, I've hit the dreaded and well-known weight-loss plateau.

The frustrating thing for me is that I haven't changed ANYTHING about what I'm doing, other than adding more mileage to my runs. I'm still eating what I want and tracking calories with Lose It...I'm under my daily calories every day. I drink lots of water and iced tea (and the occasional soda). I run every other day and have added some light weight-lifting on the in-between days. I know adding muscle mass can increase weight since muscle weighs more than fat, but the lifting I'm doing is light enough (more to strengthen and tone, not to bulk up) and I've only been doing it for the past 2 weeks. That seems, to me, awfully fast for it to already be causing an increase in muscle mass.

So what is it? Does anyone out there know? I'm going to continue doing what I'm doing because being in shape feels great and I enjoy doing it. But I'd really like to drop those last 20 lbs or so...

Any input from you readers is very welcome!